About server performance. You don't need anything big, server is ready for X thousand players by default. Just do not be paranoid about perfomance things.
I use novaline only with rewrited select querys to smart pointers, and updated boost. Tested with 2500+ online players without problem (i7-6700, freebsd 12, 32GB RAM, 6 channels).
About client perfomance. First - Do not touch ymir texture files, Second - Do not use a lot of trees and objects on the map, Three - Be a good c++ programmer for rewrite some things (btw. i am not).