You need to do some more research and figure out what you want to do before anyone can really answer your questions. The difference between the first two bikes is some geometry, parts, what size tires they can handle. The pictures might make them look nearly the same but component wise and their overall shapes are different. One is a MTB and the other is a hybrid, hybrids can be built fairly ruggedly and often borrow parts from MTBs but lack any real performance to their geometry intending for a more laid back ride, fitness versions can be a little more aggressive but usually is closer to what can make a road bike aggressive rather then a mtb. The third just looks like a basic flat bar road bike, they call it a gravel version so it probably uses wider tires though how wide I didn't look for. Flat vs drops is up to you. There are plenty of MTB trails around me that a blast to tear through on a cross bike, its just faster and more fun, being a largely sandy island that's relatively flat I actually haven't found anything I could ride with a cross bike but I haven't ridden everything out to the east. Despite that some of the things I could ride can be done faster and more carefree with a mtb and heading off Long Island there are trails that you wouldn't want to go anywhere near with anything other then a MTB, the question is where do you want to ride.
I would lean you towards a MTB since, while it might be slower at times, it really can go most any place and be more enjoyable. But if you're not hitting serious trails then a gravel or cross bike would be more fun.