I use Powerhouse Title in Baltimore: https://www.ptgtitle.com/. I don't think it should matter if the deal is seller financed, cash, or hard money; the title search and insurance process should be the same. You may want to involve an attorney for the purchase and sale and mortgage agreements though...
I agree - any title company can handle a seller financed transaction. If you start doing subto and other types then many will not touch that because of potential recourse in the future.