for the ground wires twisted together it pretty common but per breaker box manufacter they will specifed the #'s of wire they allowed in the lug holes but some local area may have addment to the local codes may required seprated ground wire to each ground lug
i think it stated in 110 but i may be wrong on this part and also in art 250 also but right now i am in middle of changing my codes a little kinda a little messy but try to get up to the speed with next code cycle soon.
I will let other chime in here too i think they will be more than happy to help you too.
Wisconsin and Paris France
"Pas de problème, il marche n'est-ce pas?" (No problem, it works doesn't it?)