This is from the first grow I did, PF tek style but with a few updates. I did a couple monotub grows a year later that went great but I can't for the life of me find any pics.
The white pebbles are perlite and the cake is mostly rice bran meal and fine vermiculite, with a little coffee and gypsum.
Cubensis is a saprophytic fungi. It decays things with cellulose in a parasitic way so if it has a food supply it will grow with varying degrees of efficiency. Pretty much all saprophytes work like that apart from some doing well on certain substrates and wood types. What you learn for oysters and lion's mane mostly works for cubensis (minus sawdust blocks which probably still do), what you learn for cubensis directly translates to being able to grow most culinary species. Even your monotubs will hold three sawdust colonies so I just grow culinary mushrooms in them.