Is there any guide of how to play properly cause I don't really understand most of the new+ stuff and the queens seem to be impassible walls only surmountable via grinding (I've already beaten the 4 bosses in the crypt).
There's no real guide per se. Essentially the core loop is: Go into the dungeon. Level up. Eventually die. Get essences containing levels and stats from your current minions. Use them on your new minions. Rinse and repeat until you beat the 2 other queens.