The gender of the class is locked, but you can use any skill with any class and all of the classes use the same skill tree but start at different locations. The most popular build of this current expansion of POE 1 was to play the Ranger class as melee.

In POE 1, each class had more access to a specific attribute, like Witch was Intelligence, Marauder was Strength, Ranger was Dexterity. Scion is a hybrid class in POE. In the trailer for POE 2, they showed that you can change the attribute node on the passive tree so that any class can specialize in any attribute. So you could choose to be a witch but then stack strength.

Each ascendancy has a special focus. The trailer shows 6 ascendancies in the early access which are women: Stormweaver (lightning abilities), Chronomancer (time manipulation, this is new idk), Deadeye (projectile abilities), Pathfinder (poison and potions), Infernalist (fire abilities), and Bloodmage (blood magic). At first glance, Deadeye looks to be an ascendancy that is meant to be played only with bows, however the class actually benefits all projectile abilities including projectiles created by spells and melee weapons.

It's hard to say right now what builds will be possible because of limited information. Many of the most powerful builds in POE 1 were from using classes in unconventional ways, like by having the Maurader be a spell caster, having the Witch fire a bow, or having the Ranger do melee attacks.