I'm going to preface this by saying that I got over my fear of roller coasters years ago and I don't find any of the ones at WDW scary, so I'm working from a very different frame of reference.
That being said, if it's the perception of being up high that bothers you, RnRC might not actually be that bad. In the dark you can't tell how high up you are or what's coming next, and as a result I often can't even tell when we're going through a loop until we're already through it. The intensity of that ride comes mainly from the launched start; it's a bit forceful (I can't ride it multiple times in a row without getting a headache) but it's not one I recall having a lot of air time.
Space Mountain is kind of a similar story because again, it's so dark you won't be able to tell how high up you are. Even though it's a smaller, slower roller coaster and doesn't go upside-down, though, I would argue that Space Mountain may actually be a bit scarier if drops bother you, since it does have a few decent ones and you won't be able to see them coming--in the grand scheme of things it doesn't have any big dives like Everest, but the drops feel more intense because they come out of nowhere.
I found 7DMT to be very mild; it's designed as a roller coaster appropriate to be a kid's first "big ride." The rocking cars actually lessen the forces on the riders, so it's quite gentle. As for BTMRR, I'd suggest requesting a seat in front if you're nervous, as the back is much more intense.
Re: Everest, the two big heights moments I can think of are on the lift hill going up to the top of the mountain--nothing too exciting is actually happening at that moment but you're going to be pretty aware of how high up you are--and then of course the big drop. You both do and don't see the drop coming, if that makes sense. You know you're going into a good hill, but because of the way it's set up as you exit the interior of the mountain you can't really see the full extent of the drop until you're basically in it.
. I'm not really a coaster person at all (7DMT and Splash are my favorites and the perfect speeds for me! lol), so EE isn't a ride I'd probably do multiple times in a row or even necessarily every trip, but it was fun! Didn't seem nearly as "bumpy" as Space Mtn. or Big Thunder. Also, I hate upside downs, I don't remember feeling that way at all on EE.
