Beginning to end wheel/tire questions

Hi I’m gonna probably have alot of questions on my tire and wheel upgrade to my quad so started a new thread. As far as the tires go I think I’m pretty sold on the bighorn og’s as I believe they are the best match for my riding as far as size that’s where the questions start from what I’ve been reading I think I want to stick with a 12 inch rim width wise I could use some opinions on that I know a friend of mine just got itp rims with a 8 inch tire and the rims seem to stick out to much and might bear alot of side impacts. Also not sure what size to get I’m either at 25 or 26 on this I do like the look of the bigger tire a little extra clearance would be nice but if I go with the 26 I’m just not sure if and how much power I’ll be losing and don’t know much about the shims and Springs but will that cause any kind of reliability issues. I’ll have more on the wheels but I’ll break it off here