Possibly you would not. To each their own. I wanted a slightly larger tire to fill the wheel well so that's what I went with.
There is a noticeable difference in size -
I went 2" on the front for a slight rake. I had to go with replacement intrusion beams and modify buy mudflaps to eliminate the rub. I can't say if a 2.5 would give you the clearance you would need. I'd search the forums and see who else might have that combo.
The ring is sometimes needed with after market rims to center the wheel on the hub and align it with the axle. The rings are vehicle and wheel specific. For the Method rims I bought, these are the rings that fit -...
Yup that's correct. And no spacers. Just the hub centric rings to help keep them balanced. Tires came inflated to 75lbs, but I aired them down to 60 for a bit more comfortable ride.