Do One-For-All users have different training experiences? While training his successor, All Might is often surprised by Midoriya's abilities (or lack thereof) to control One-for-All. He notes things like, "I guess you can only use 5% of this power right now". 
Were All Might and previous users just more adept in adapting to this Quirk?
Yes, the other successor's for One-For-All where handpicked by the previous users among the most fit to use the quirk. Gran Torino mentions that even though Toshinori/All-Might was born quirkless, he possessed great resilience and endurance to maintain One-For-All power.

Midoryia had no previous training nor did he had good constitution or muscle strength to keep up with One-For-All's great stress upon the body. That is why All-Might has those often remarks about him.