Returning solo player here (level 32). With class mastery and subclasses does one lock you out of the otherv

So im a returning player on a necromancer using the baneful summoner preset. I however know we can like subclass now but with the new update there’s “class specific masteries” now everything i have seen on it emphasizes “pure to your class”

So how do these two systems work together and what should i be aware of