Shadowplay doesn't "max out" at 720p - should be able to record in your native res. Or are you talking about the youtube side? Yep, you are. Don't mind me, no idea.
check that you're exporting something like this:Uh YouTube maxes out at 8k... what problem are you having CB?
if youtube isn't giving you a 1080 version its probably because the file you're giving it is below that res
for midair i don't think you need to capture or export higher than 15 Mbps (for 1080 vidya footage). it just eats up your hdd, takes longer to encode, longer to upload, longer for youtube to process and gets turned into ~12 Mbps anyway.