Lots of fantastic information in here. It honestly makes me feel happy with how informed you guys are.
Here are the types of shoes that are intended for which types of surface.
IC, flats - indoor court, think futsal and older astroturf (carpet)
Tf, nubs- turf, think astroturf (carpet) and some 3g turf (more grasslike with the pellets)
Ag, molded studs that are shorter and more of them- 3g turf and some dry grass
Fg, molded studs of normal length and normal amount- dry grass and some wet grass
Sg, studs of longer length and less of them- wet grass
Realistically the perfect all around boot for SoCal kids is going to be the AG soleplate. It has the most crossover for the types of fields our players are on. Ag soleplates have more studs of reduced length to limit the locked in feeling of playing in turf in fg boots, it is hard to explain but once you’ve done it you know the feeling. This is where it gets tricky as causation for injury hasn’t been proven between using fg boots on turf, but it certainly has correlation.
Sg realistically will never be used unless there is a large amount of rain or they are traveling somewhere where there is a lot of rain.
Fg is what we see the most of. They are fine for grass fields and okay for turf, but the ideal in my eyes would be to slip once or twice in ag boots on a harder field than impact your joints more heavily in fg boots on turf.
I hope this helps!