Steak butter? To use or not to use? also a recipe if I should use it, would be for 2 filet's (not sure cut matters)

A good cut like a rib eye done medium rare should have enough wetness to allow the flavor of the meat be supreme. Steak houses often pop a pat of butter on top to make the meat look better.
It is all your personal taste - if you like butter, use it. I prefer the steak naked, properly seared with a tasty crust, and save the butter for a nice piece of bread.
Like with lobster and drawn butter you can always serve some melted compound butter on the side to dip the periodic piece of meat into.

We ended up grilling them in a scorching hot pan with butter in it
Delicious!!!

If you're doing plain butter, though, definitely go salted over unsalted!

We often grill our steak already rubbed with herbs and will melt a pat of butter on top as they rest. We typically cook rib eyes which are a fattier (tastier) cut than a fillet, but I think if you are already indulging in a tasty steak, a pat of butter (plain or compound) is a good thing.