What you want is just a hoster which offers you at least 2 dedicated physical cpu cores or even a complete machine. The cpu should be Intel, ideally last gen and high frequency, like the xeon processors targetting workstation use or desktop core-i7. Single thread performance is key for minecraft servers.
The hoster can't do much about performance anyway besides providing decent hardware and not overcommitting on mc server instance per cpu core count.
You as an admin can use tools like OPIS from ProfMobius to locate where slow setups are on the world, educate your players about what's causing issues and tune your mod+config selections to avoid issues. The worst are entities, avoid mob spawners, keep the number of smart mobs down (golems etc.), transporting entities (including dropped items) with water or even through portals. Use personal anchors instead of normal always-on chunkloaders or better none at all. Don't have excessive redundant machinery. Avoid fast travelling (like MPS flight) while you are not alone on the server.
If this doesn't suffice I have a mod in development which can generate more sophisticated data about performance issues, but it isn't really user friendly yet.
Before someone mentions thermal expansion as a "solution", TE is only insignificantly more efficient, but it has continuously had severe bugs in its conduit code since the beginning, causing memory leaks and sporadically performance bugs bringing servers to a halt.