It’s already been said ,but what ever level you and opponents have the most fun with is likely the best.
Though from a balance and competitive standpoint its almost certainly 2300 points. Playtesting is done at a few levels but the vast majority was done at 2300 for the initial edition launch and the new Clash of Kings coming out November 2021.
So while there is some feedback from other point levels most of the fixes, changes, edits and etc are based on testing from that point level.
That being said the testers come from around the world so it’s tested in a lot of different metas, in any given meta certain lists can be way weaker or stronger if no one locally plays the counters to said list that would perhaps encourage a different approach.
It’s really hard to completely balance everything, it’s fact it’s probably impossible but as playtesters we tried to get as much data to the RC as possible to get everyone the best game we could.