If you’re wanting to tailor things very specifically, I’d probably recommend one of the frameworks - either Foundry, Foundation, or UI Kit as they give you a blank canvas to work from. It’s a bit more of an upfront investment (and perhaps more of a learning curve) but it gives you control over the look and feel much more than a theme.
I have a preference for Foundation but all three are capable.
I know Stacks4Stacks.com does some custom work so you could try @willwood if you wanted to investigate a custom solution.