I was wondering about 7DMT for solos - I figured they would probably fill every seat, since there are individual restraints.
I have been going solo during lower crowd times in early February. I have not done EE or RnRC, but have done Test Track (single rider) and obviously been seated with other guests to fill the cars.
I have not been seated with anyone on a ride with a single restraint/no restraint and a "2-person" row (BTMRR, Splash, etc) or a ride vehicle that is usually for 1-3 people in the same party (HM, Pan, etc.). On Pooh, I've always had a seat to myself, with another party in the seat in front or behind.
On the boat rides, I have more often than not had a seat to myself (usually the narrower seat in the front or back row), but sometimes been seated with another party of 1 or 2 (so not cramped). On the Safari, I've always been seated with another party of 1 or 2 - we each have a "side" of the vehicle and again not cramped.
There was a thread here, though, from late last year I think, where people reported being packed into rows with strangers on rides like Pirates, so I'm sure it depends a lot on the crowds.