Best vanilla version to not overload the server

Hi everyone, I have just discovered this wonderful platform and I have already tried to create a server in the latest version of the game (1.15.2), it worked but the only problem is that there is a bit of lag and on the logs i can see the warning that the server is overloaded. i saw that this is due to the very recent version of the game so... which is the best one to play (quite recent) that goes on smoothly?

Thanks for the help,

Bye.

Well, thanks for the immediate answer! I will try these ones. Keep up the good work.

Bye.

One last question, i would try to install PaperMc (before eventually switching to 1.12.1), can I ask how to do that? Is there any guide?

Ok perfect