The seat can make a huge difference. Cheaper kayaks typically have very basic (and fixed position) seats. The seat in my hobie outback is fantastic and makes long days easy. Stability also matters. I can stand in mine with no problem. This is not possible in all kayaks.
I also prefer a sit on top model for fishing. However, the highly stable models that make for good standing/fishing also don‘t track as well as the longer, narrower ones for paddling (Sometimes called sea kayaks). This makes a rudder very helpful on a fishing model. Not having a rudder makes controlling a fishing kayak, even in a light breeze, challenging when you are fishing.
As stated previously, weight is a consideration. If you plan to transport it on a car or a truck rack (high overhead lift required) I’d stay away from the big fishing models (like the outback and pro fisherman). I transport mine on my diamondback cover on the back of my truck, but it can be a handful to load and unload from that height. I also use a cart with two wheels to move it around To/from the waters edge or ramp. When taking both kayaks out on the water (with my wife) I use a trailer to keep loading and unloading easier.
i went to a demo day before deciding on mine. I’d suggest getting in a few and paddling/pedaling around to see what suits you. For me, my setup with the pedals is great and lets me cover a lot of water relatively quickly. Your situation may be completely different than mine however.
The options and features are many, and can get to be a bit overwhelming and confusing. Starting with a lower end one first and then having that as a second/back up option if you decide to upgrade later also isn‘t a bad idea. But, they are all pretty expensive compared to what they were a few years ago.
lastly, I did see a guy with two carbon fiber canoes that he carried on top of his RV. Those we’re crazy light like 13-15 lbs, but I’m sure they aren’t cheap. Sitting a little higher from the water surface can be a benefit when fishing.
Best of luck. Let us know what you end up with.