The last I read from Google about 8 months ago was that it works a lot like any other streaming service: if you have the basic or free plan, you don't get anything but 1080p max. In order to actually see anything in 2k or 4k, you have to have the premium service.
If you do not have the premium service, you can still upload 2 and 4 k video, but you'll never see it. Only people with premium accounts will. So unless you have a premium account, it's an exercise in futility to upload anything beyond 1080.
In fact, even if you do have a premium account, it's still pretty worthless because 99% of the people that are going to watch your videos are doing it for free, and of them most are on devices that don't support 2k or 4k to begin with.
....