Sweet potato pie can be made using the same recipes as for pumpkin pie. Of course the sweet potato has to be cooked and mashed until smooth first.
When the pie is made using a pumpkin pie recipe, the flavor is similar. That being said, you can do a few things with sweet potato pie that is not normally done with pumpkin pie. You can flavor the custard with maple syrup for instance, or add orange zest to the custard. It doesn't have to taste like traditional pumpkin pie. As it is a custard, the texture is nearly identical to pumpkin pie. Yep, I've both had and made sweet potato pie.
I once was given a slice of bean pie, made I think from great northern beans. How this was done, I don't know. But it was also very similar in both texture and flavor to pumpkin pie.
Oh, a tip. I once had too much pumpkin pie filling for the two pie crusts that I had made. I added flour and baking powder, with a bit of cooking oil to the filling mixture. I then cooked the batter in my waffle iron. That made some really tasty waffles, with syrup and butter.
Seeeeeya; Goodweed of the North