I've been running iOS 14, on an iPhone 7 Plus, and iPad Air 2, and have had no problems with either.By Jove, I do! ..... I did. Now 14 shows up! Thank you @C DM. Hmmm... To upgrade or not to upgrade, that is the question. 14.1 has a nice ring to it. Once Catalina-ed, twice shy.
The iPhone was an in place upgrade, while the iPad was a restore and clean install. Both devices have functioned perfectly in my circumstances. I think iOS 13, and Catalina were the most likely to cause issues for me on day one, out of all the apple operating systems I've used.