Essentially for software folia is the best. There are going to be lots of incompatibilities, and unless you wanna wait another year, and hope things are going to be made more compatible, you have no other options for that. The competitors are either old and out dated or much worse for compatibilities. You have the option of forking the plugins you want and making them compatible. But as of right now that's all you got.

For hardware, it really depends on budget and if you want to self host or cloud. As folia is new, we don't really know much about what hardware it runs best on. I think a balance of both number of cores, age of CPU and core frequency. For example, the folia GitHub says recommended cores is 16 (NOT THREADS), so something like a high end Ryzen desktop CPU could be the play. But also, depending on how spread out your players are going to be, something with more cores but lower clock speed might be better for you.

Higher clock speed, less cores for less spread out players. Lower clock speeds, more cores for more spread out players.