I'm fairly certain that you may not convert an inherited IRA.
You do have to withdraw from the inherited IRA; since it sounds like you inherited it pre-2020, you are likely withdrawing based on an RMD schedule on your life time.
You can turn around and contribute to your Roth IRA if you want to (and have income to qualify), and the RMDs from the inherited IRA can give you the cash flow to do so, but you can't directly do inherited IRA -> Roth IRA conversions.
The general calculus, and there are a zillion caveats, but generally if you figure what your marginal tax bracket would be when you're in your early 70's and have RMDs and SS (and whatever else), then converting enough now to get to approximately that same bracket is usually the recommendation. It depends on a lot of factors though.
200% FPL for a single person is still in the 12% bracket, right? You might see what your marginal rate would be (including loss of ACA subsidy, if applicable) at the top of the 12% bracket. Above that is 22%, and with the ACA subsidy loss it becomes a tax hump that's big and wide, thus hard to get motivated to swallow.