Yes if you want to decrease the file size, using 30p and perhaps no more than half the bit rate of the original is good. YouTube doesn't allow over 30p although I really, really, really hope that's at least in the works. I mean they offer huge resolution sizes like for people who shoots in 4K but not 1080 or 720 60p.
Also, at least when you post 1080p videos, people will choose how high they want to view the quality depending on their connection so it's not like if you upload in 1080p, it will automatically stream in 1080p. It will still start at around 360p or 480p.
Anyway, if you don't mind spending more cash, one option to upload the biggest files possible and not worry about the speed is to increase the speed of your connection. Maybe an extra $10 per month can be a huge difference in speed.