Oddly enough, I have a family member who had their dentist recently suggest that they either use a pacifier at night or a night-guard to cut down on their grinding
In all honesty, once you get your adult teeth, it takes a lot to damage or alter them in any way. I've used my adult pacifiers for years now, semi regularly too, as I try to regress every weekend and my dentist continually tells me how healthy and perfect they are. I have heard of people developing a slight under or overbite using adult pacis, but I have yet to hear that pacifier use as an adult increases the likelihood of grinding. So, I would say that your grinding issue is unrelated to your pacifier use.
As to your question regarding a baby pacifier vs. an adult pacifier, I would scale up my friend
Baby pacifiers might not effect your teeth any more or less than an adult sized one, but from experience, baby pacis are never very comfortable (at least in my mouth anyways) and they can sometimes make your teeth hurt because they don't sit as naturally in a big persons mouth. There are Adult Pacifiers, Nuk 5 and Nuk 6 in particular, like the ones sold through Babypants or Little For Big, that aren't massive in the slightest. A nuk 5 or a nuk 6 is literally just a larger version of your standard baby pacifier, so it will sit in an adult mouth incredibly naturally and the shield is a little bigger too, which contributes to a much more babyish look when you are using one. Also, as I said at the top of this, if you are having grinding issues, an adult paci could very well help prevent and alleviate that.