If you are target shooting it makes sense to limit the draw force since your focus is maximum accuracy. The same mindset can be applied to the bands, by lowering the strain the bands are more forgiving. You aim using the fine control muscles, if draw force is varying a lot vs position it’s very hard to be accurate. ‘Slower’ bands also make the release is much easier this affects accuracy a lot. With the pouch, you maximise feel. Match the ammo to the above and it’s pretty small. But ultimately it’s all personal preference, if you are confident with the setup you can practice more.
There might be something to be said that smaller holes in the target is a good thing. After 3-5 shots, I was passing every follow up through the hole. 1/4” or 6 mm was the fashion a few years ago, down from 8 mm.
For competitions it would depend on the rules. Chronographs tended to need shot of a certain size to work. So the speed competition used 6 mm or 1/4”. The brand of the slingshot rubber mattered a lot, some rubber was just faster than others. 100% latex was very highly rated… You didn’t go faster. Thinner rubber tended to be faster (but this topic is complicated!). Hot rubber was faster too (heating wasn’t cheating!). High strain, highly tapered bands, very small and very light weight pouches help too. Plus a long draw was essential too.
For power competition there was a minimum speed to qualify (180 fps). I would have set the speed at ~171 fps, so each gram would be 1 ft-lb. Also note chronographs have their own minimum speeds some around 100 fps. With big energy figure: It’s a lot easier to accelerate a much bigger projectile from zero to slow, that to accelerate something small to fast. Large ammo also gets really difficult to accurately release or pass through the fork. So serious entries where casting their own lead slugs. The draw force and holding the fork of the slingshot true is also a major problem, It’s not just the strength in your biceps.
With hunting things are different again, but the politics was strong with this topic. How you trade speed/accuracy at range vs momentum is largely your business. You want the shot fast enough to reduce your hold over target (compensating for drop), but not so fast it your leaving momentum on the table so to speak. My take is: If you were squeamish over a chronograph you weren’t good enough.