I don't think you'll have any problems with the personal item (cabin bag) being oversized. I don't fly United but none of my bags have never been sized before boarding. Also, I'm glad you got the two wheel version because the spinner version can be tipsy and fall over sometimes. The spinner is just more maneuverable. And you probably won't see many airline employees with spinners. Once you start using that cabin bag, you'll love it for it's versatility. Enjoy!

Also, the built-in suiter....I never use it for suits. I just lay all my regular clothes in there pants/shirts whatever and fold over the sleeves of shirts and roll the suiter up and that's where all my clothes stay except under clothing. I don't out them on hangers ... it's not necessary. The suiter really reduces wrinkles no matter what clothing you lay in it.