Nobody here can answer if it’ll bother your neck, as everyone’s physical issues are different. I’ve had surgery on both knees, one hip, have a herniated lower back disc and neck bulges…but none of the rides bother me. I don’t think any ride at WDW is so violent it would actually give an otherwise healthy person “whiplash”. But it doesn’t mean they won’t bother you.
The backwards part of EE doesn’t force your head forward, IMO. I’d say it lasts about 15 seconds, maybe a bit less. It does make you feel like you’re flipping over, but it’s actually just a steeply banked turn (uphill, I believe). I don’t find the ride to be exceptionally “jerky”, probably on par with a lot of other similar coasters.
RnR is incredibly smooth, IMO. The initial launch is fierce (best part of the ride), but if you simply rest your head back in the seat before launch, your head won’t really go anywhere. You don’t need to press it back, that’s unnecessary, IMO…just rest it back and relax…the force of the takeoff will keep it back for you. The rest of it is quite smooth. As a PP mentioned, Dinosaur and Space Mountain are pretty jerky in that they have quick motions back and forth. BTMRR is also very jerky, IMO. TT has a few spots where it jostles you back and forth, but nothing crazy.
You mentioned you’ve done BTMRR and Dinosaur. If you can handle those, then I’d think you can handle anything else.