Yes, that's the general rule and like @Ποσιδονας wroteGenerally the rule is lower quality, easier training. So if its fats trainer it's gonna be easy to train him.
it's correct but only for the newborn players (academy or from the market).A 5* 80% academy 14 token player need 35 greens to get a sa.
A 5* 95% ft, new player, need 50 greens.
If it's about a 85-90% q player you had from previous season but has some skills very high, then you must follow the post #3 example and find the drills with low skills