Are you looking for an RPG engine or a game engine you could build an RPG in? Generic engines like Unity and Godot don't care about you tile size. RPG Maker MV uses 48x48 I believe. Not sure if RPG Maker MZ changes that. I think RPG Maker MV can use a different size by using plugins but I have not tried. (I did start writing my own which used 64x64 tileset but never finished the combat system.)