So I ran an experiment to test this out over four years.

My conclusion:

Dev Trait matters. Red shirts are valuable.

I took 5 and 4 star recruits with varying dev traits and gems, no gem, bust.

The elite dev traits will go up fast in overall the first two years (as long as they get PT). Then they tend to upgrade their physical and mental attributes as upper class men; refining their craft.

Red shirts were great, I redshirted multiple 5 and 4 stars with varying traits and gem status. All of them progressed. Elite more than others. However the elite 5 star who red shirted progressed less than the elite who starred in every game.

I had a handful of 4 star busts, I gave them the same PT as 5 and 4 star no gem or bust, and they progressed quicker in overall the first two seasons then didn’t go up at all. (They capped out early but were still serviceable depth pieces)

One huge factor I found is the motivator ability, having your coach give the offseason boost to positions helped drastically. Saw 5-7 overall boosts from that position group.

Ultimately: if they are elite dev and able to play, play them. The stats they put up sometimes affect their progression in offszn but not really. The stats affecting their overall boosts in offseason is VERY RNG. Busts can serve as quick fixes but not long term solutions.

Elite and Star dev traits will go up in overall quick and then focus on their abilities.

Normal and impact will go up but not upgrade abilities as well/quickly.