I've been using PaperMC with optimized configurations from YouHaveTrouble's GitHub, and 30+ plugins can already crash the server if there are 5 players, most likely loading and unloading chunks along the way.
The sweet spot I see is around 20-26 plugins currently. A workaround I tried is to modify Paper's unload chunk much faster to free up RAM as the primary reason for the crash is Out of Memory. How about you?
I seek the optimal amount of plugins per server for an SMP with friends.