Hmmmmmm............Just one?
I do things a little bit differently I guess. For the past couple of years I've only used a 5wt and a 3wt. I did have a TFO 7wt but the Eleven Point river ate it. Long story. But I never really liked it. It wasn't the rod, but it didn't match my casting style.
Is a heavier weight rod better for casting larger flies for bass? Maybe. Oh ok it probably is. But I have a really nice 5wt with a really good line and I seldom feel the need for anything more. However I will probably add a heavier weight rod in the spring....maybe.
Truth is, I like my 3wt so much that I spend a lot of time smallmouth fishing with it. Have I lost some nice fish because of that, oh yeah, but it was probably more of a result of the specific moment than that rod not being able to handle the fish.
Starting out fly fishing I would go with a 5wt. It will give you more options in the fish you catch. You can have a lot of fun getting started just dinking with bluegill. It's a lot of fun. Now if you try that with a 7wt it's going to be laike dragging them in on a broom stick.
I have a buddy that started fly fishing for smallmouth about the same time I did. I bought a nice 5wt, he bought a 7wt. Now several years later I still enjoy my 5wt and he doesn't fly fish anymore. From the conversations that we've had, if he had a different rod he would probably still be doing it.
You don't have to throw a big heavy wind resistant fly to catch smallmouth.