Just how configurable is Filament?

My work is wanting to use Nova or Filament, and we're weighing our options.

We need to be able to have a highly customizable UI, to the point where I don't think Filament has enough options to cover our needs.

Additionally, we already have an admin UI that we've built over the past 10 years, but it's not programmatically defined, and 30% of our codebase is blade templates that are basically the same. But we'd like something that can be partially integrated.

We like Nova's tech stack, as it's powered by an API, which means that we can build our own UI that interfaces with Nova's API. I've done something that this before, and it wasn't too difficult.

However, if Filament is actually configurable enough to get the UI we want, without have to rewrite the majority of its components, then I'd prefer to go that route.

To be clear, we're talking a completely different layout, theme, specifics on how input fields look, positioning of buttons, a different action selector, and more.

In short, we're wanting to replace existing UIs with very minimal changes to the look and feel.