Hi Loren
Where you may find the biggest difference between 11 and, say, 16 is in the speed of processing. Shadow files will be essential, and on versions prior to PD15 they were notoriously slow to process.
4K video takes a lot more computer power, so if your PC is not at the top level you may experience jumping and the like on the timeline. While 4K is great, to get the best out of it you will need a 4K TV or whatever, that can view it. Otherwise there is no point having 4K.
IMHO I would upgrade to the latest PD version to obtain optimum speeds. Sometime soon I suspect PD17 will be on the market so you could keep an eye out for PD16 bargains.
I only shoot in 4K and I use PD16 without any real problems, but I do have a reasonable spec machine.
Why not post a copy of your PCs DxDiag file so that other members of the forum can comment on your combatability with 4K
I hope this helps you
Robert