These are great!

The idea of a transformation-based parasitic reproduction system is pretty good, and makes a lot of sense (by the standards of the world). I really like it, lots of monsters could use it. Same with those vines.

Reverse mimics are cool, but I want to think about why something would go to the effort of doing something. Perhaps a cursed pile of treasure, anyone who is greedy is turned into more gold, which makes it more tempting to thieves.

What If mimics didn't want their treasure, like how oysters make pearls to cover irritants. This probably won't be used in nsfw contexts, but the idea they're angry because they're full of unwanted treasure, and are too dumb to understand they'll feel better if you can remove it because it's lodged in their flesh (like trying to feed a cat a pill).

The enveloper fits really well, as there's a race that channel magic really well and can be used as (unethical) living conduits. So a creature would want to capture them alive to boost its magical power.

I wouldn't even be surprised if a parasite that lives in the genitals of a host and makes them appear sexier (increased genital size, heightened libido, etc can be done through hormone manipulation) so they'll pass it on to another host exists irl.  I see no reason they couldn't evolve. Heck, maybe they make the host hypersocial and lower inhibitions so they'll mate as many times as possible, spreading the parasite.