They can be made to be extremely hostile like Johnny Vindicators and Zoglins if you want, and can be made to spawn naturally (by default, rarely) in Crimson Forests and Nether Wastes
Brutes spawn in Bastions, like they do in 1.16.2
You can also configure it so they can spawn naturally (by default, rarely) in Crimson Forests and Nether Wastes
