I wouldn't call GhostRider extreme, but I've also been on a ton of coasters, so it can be hard for me to gauge how others will feel about rides. What I will say is that it's pretty much a straightforward out and back wooden coaster in an L shape that doesn't do anything super radical, just has a lot of hills mostly. It's not entirely dissimilar from something like Incredicoaster (without the launch and loop) on paper, but a little bit more aggressive. Additionally, it's impressively smooth for a wooden coaster (and definitely smoother than the Matterhorn or Sky School), so roughness isn't really a factor IMO.
I think it's a lot of fun, and it's one of those rides that seems to please most everyone-I haven't seen or heard of anyone coming off GhostRider since its big refurbishment in 2016 that didn't seem to have a good time. You can always check out a video and see if it might be something you feel comfortable jumping into or if you want to come back to it a bit later.
Here's a POV that you can check out so you know what to expect.
If you're looking a tamer coaster to start out with, Jaguar is indisputably a coaster but is only slightly more thrilling than the monorail IMO. Pony Express is pretty basic too, with the only radical thing about it being the Tron-esque riding position. Coast Rider is comparable to, but slightly more intense than, Sky School (but with a dumb knee restraint that might make it harder to ride comfortably). Montezuma is pretty tame, but is closed for refurbishment. Xcelerator is a bit intense, but has been closed for awhile, so probably won't be open any time soon. But ultimately there's nothing at Knott's that, from my perspective, is super extreme, with HangTime probably being the most frightening-looking from ground level, but even that is very smooth.
It's a Cedar Fair park, so expect pretty much everything to have a seatbelt in addition to whatever the primary restraint is, usually, but not always, fastened first. They have loose item storage in every coaster station on the exit side of the platform.
RE missing things in Fiesta Village: though I love Montezuma, in reality you're not missing anything super significant.