On everything low is 20 fps in fight but in menu the fps lifts up to 80 fps on the demo but the free version is a bit heavier it is 45 fps on the menu everything is low then in game it's 15 or 13 or 7 fps depending on the maps and the characters
I think the demo experience is going to be pretty much as good as it will get, ultimately. To go a bit more in detail: Here I'm depending on the game engine itself (Godot) and how it runs on various hardware (it's like Unity, basically, and I have no control over it and its rendering performance). There are some things also in the game that probably demand more graphics power (they are a result of high customizability), which are this way by design and not 'fixable' (they increase the number of draw calls, making graphics more expensive to render). I'm sorry there's no better news to give. But I hope that the demo level performance will allow you to still enjoy the game, even if maybe not all the arenas.