In the phrase omnimoda potestate antistes, should any words be capitalized? And how would it be translated? It is in reference to a 16th century bishop who considered himself, omnimoda potestate antistes.
Antistes literally means something like "stander before", from ante "before, in front of" and stare "to stand", and usually means "overseer" (compare president, literally "sitter before", from prae "before" and sedēre "to sit"), but in the context of Christianity it's a title that's either usually left untranslated or (more commonly in the Catholic Church, I think) translated as "bishop".
Omnimodā potestāte is the ablative of omnimoda potestās (the macrons are not usually written, but I've added them so you can see omnimodā has a long a in the ablative but not the nominative), the "authority of all kinds". The use of the ablative here is kind of unusual but suggests to me that his position as antistes comes forth out of the authority of all of kinds, which would presumably be God or the Church. (If it's an instrumental ablative, on the other hand, he's assigning himself, or rather the office of antistes, authority of all kinds, which seems a bit brazen.)
The whole construction can be translated as "bishop of the authority of all kinds". As for how it should be capitalised, the Catholic Encyclopedia seems to use Omnimoda potestate Antistes, which I see no real reason to contradict.