Training pants questions

[peanut520]

I need some help with training pants.

-DD is 15mo and is willing to tell us if she needs to go or just went or start walking towards the bathroom where her potty is
-She is willing to sit on her potty or the big potty if you hold her or sit behind her
-She is thin, 20lbs but 31 inches tall
-We currently use Seventh Generation sz3 dipes

1. Is it time for training pants?
2. Is disposable the best option or should i go with "regular" training pants (cotton underpants with the extra padding)
3. How should disposable training pant fit? sg training pants start at 2t-3t. i called them and they sent me 2 to try for size but i think they are quite saggy.

all suggestions are welcomed!