the Atlas is basically too slow (48 km/h or so) to be useful in mechwarrior 5 imo
Okay, there's other reasons why it's not good and the speed isn't the problem, it's more the lack of guns. You are significantly better off with the Stalker STK-3F with 4 medium lasers, 4 SRM6s, and 2 PPCs, and the Banshee BNC-3S with 2 PPCs, 1 AC10/LBX10, and fill the rest with medium lasers though I don't remember how many because I don't remember the vanilla MW5 mechlab hardpoint limits for that variant because vanilla MW5 mechlab is pretty trash. There's only a very small handful of mechs that can out pace the STK-3F and BNC-3S, but all of them either come way too late to actually matter, or you can only get one of them per playthrough.
without a risk of overheating
This isn't MW3, or MW4 where there's degrading effects for being at higher heat and the possibility of shutting down before filling the heat bar, MW5 uses MWO's heat system which means the only heat point that matters is the very last one. Also because there's only like maybe a handful of actually threatening units in vanilla MW5, shutting down from overheating is nowhere near as bad as it is in MWO or even previous titles. Besides, heat doesn't matter if the other guy is dead, and all the harder encounters in MW5 (both in vanilla and the DLCs) are burst DPS races.
countless stalkers lie as smouldering wreckage in the wake of my MW5 Battlemaster squad with all rear armor reduced to 10 and all other armor maxed out. if nothing else the snail pace max speed makes piloting the stalker painful imo. i tried DPS builds for so long before just armormaxxing, now i literally never even lose a single point of structural limb damage on any mech any more, just armor damage to be cheaply repaired. if you play smart nothing will get behind you long enough to pierce the 10 armor points and the consistent quad M lasers + dual L arm MGs + SRM6 (sometimes SRM4 with more ammo) + occasional melee attack (i love that they added mech punching in a free update with their paid DLCs that introduced melee weapons) with plenty of ammo and heat sinks has been enough to shred enemy forces with much more tonnage than my unit. i even deploy overtonnage on easier missions and eat the deployment cost increase because i never get damaged enough to need expensive repairs or replacement weapons/ammo/mechs. as much as i like PPCs aesthetically and conceptually, every time i tried a mech with a PPC i was overheating constantly or agonizing over lethargic cooldowns during climactic fights, unless i removed most armor and weapons to put in heat sinks. the cooldown for PPCs is already so slow without having to take a 30 second break every time i get into a real fight. larger autocannons i kept running out of ammo and never had enough weight for the armor, ammo, weapons, and heat sinks i needed, and unless you use an ultra autocannon and risk jamming it, they have cooldowns just about as slow as the PPC, and are very unsatisfying to use. i wish they were all automatic like real-world autocannons, i hate the slow tank-cannon style loading times. the Banshee worked out decently but they are just so much uglier than a Battlemaster imo and not that much less time to kill against enemy mechs. I think i do better with beam weapons usually in MW5, i can kind of guide the aim-assist to specifically target the cockpit window for insta-kills with lasers, i'm often surprised when nothing but my chainfiring quad short burst M Lasers gets a bizarrely fast kill on an enemy Awesome or Mauler or Atlas, while with autocannons or LRMs i can never seem to consistently hit the same place, with the damage getting spread around multiple body parts and sets of armor and HP.
edit: also it might be 'cheating' but i play with the optional FPS-style controls instead of the default classic tank style controls, it doesn't make sense to me to have a bipedal robot that can't easily strafe and handles identically to a very tall tank. idk exactly how that might break the default enemy AI, it definitely makes juking back and forth to avoid damage easier tho.
Okay, there's other reasons why it's not good and the speed isn't the problem, it's more the lack of guns. You are significantly better off with the Stalker STK-3F with 4 medium lasers, 4 SRM6s, and 2 PPCs, and the Banshee BNC-3S with 2 PPCs, 1 AC10/LBX10, and fill the rest with medium lasers though I don't remember how many because I don't remember the vanilla MW5 mechlab hardpoint limits for that variant because vanilla MW5 mechlab is pretty trash. There's only a very small handful of mechs that can out pace the STK-3F and BNC-3S, but all of them either come way too late to actually matter, or you can only get one of them per playthrough.
This isn't MW3, or MW4 where there's degrading effects for being at higher heat and the possibility of shutting down before filling the heat bar, MW5 uses MWO's heat system which means the only heat point that matters is the very last one. Also because there's only like maybe a handful of actually threatening units in vanilla MW5, shutting down from overheating is nowhere near as bad as it is in MWO or even previous titles. Besides, heat doesn't matter if the other guy is dead, and all the harder encounters in MW5 (both in vanilla and the DLCs) are burst DPS races.
countless stalkers lie as smouldering wreckage in the wake of my MW5 Battlemaster squad with all rear armor reduced to 10 and all other armor maxed out. if nothing else the snail pace max speed makes piloting the stalker painful imo. i tried DPS builds for so long before just armormaxxing, now i literally never even lose a single point of structural limb damage on any mech any more, just armor damage to be cheaply repaired. if you play smart nothing will get behind you long enough to pierce the 10 armor points and the consistent quad M lasers + dual L arm MGs + SRM6 (sometimes SRM4 with more ammo) + occasional melee attack (i love that they added mech punching in a free update with their paid DLCs that introduced melee weapons) with plenty of ammo and heat sinks has been enough to shred enemy forces with much more tonnage than my unit. i even deploy overtonnage on easier missions and eat the deployment cost increase because i never get damaged enough to need expensive repairs or replacement weapons/ammo/mechs. as much as i like PPCs aesthetically and conceptually, every time i tried a mech with a PPC i was overheating constantly or agonizing over lethargic cooldowns during climactic fights, unless i removed most armor and weapons to put in heat sinks. the cooldown for PPCs is already so slow without having to take a 30 second break every time i get into a real fight. larger autocannons i kept running out of ammo and never had enough weight for the armor, ammo, weapons, and heat sinks i needed, and unless you use an ultra autocannon and risk jamming it, they have cooldowns just about as slow as the PPC, and are very unsatisfying to use. i wish they were all automatic like real-world autocannons, i hate the slow tank-cannon style loading times. the Banshee worked out decently but they are just so much uglier than a Battlemaster imo and not that much less time to kill against enemy mechs. I think i do better with beam weapons usually in MW5, i can kind of guide the aim-assist to specifically target the cockpit window for insta-kills with lasers, i'm often surprised when nothing but my chainfiring quad short burst M Lasers gets a bizarrely fast kill on an enemy Awesome or Mauler or Atlas, while with autocannons or LRMs i can never seem to consistently hit the same place, with the damage getting spread around multiple body parts and sets of armor and HP.
edit: also it might be 'cheating' but i play with the optional FPS-style controls instead of the default classic tank style controls, it doesn't make sense to me to have a bipedal robot that can't easily strafe and handles identically to a very tall tank. idk exactly how that might break the default enemy AI, it definitely makes juking back and forth to avoid damage easier tho.