The short answer is no and a slightly longer answer is that I would recommend that anyone using Firefox disable DoH and use Sonic's assigned servers. [ ... ] Firefox's position makes sense if you believe that all ISPs are bad actors. :/
You are, of course, correct that Sonic-local DNS servers will out-perform HTTPS requests to Cloudflare or whoever. However, I wonder if you're missing the larger philisophical issue that Mozilla is attempting to address. DoH doesn't mean you distrust your ISP -- DoH means you no longer have to. (It also means you don't have to trust your firewall vendor, or whoever's running the open WAP at your coffee shop.)
Personally, I think it causes more problems than its solves. DNS is hierarchically distributed and relatively resistant to disruption, whereas DoH creates single points of failure, and high-value targets for disruption and infiltration. Also: There's no guarantee that Cloudflare will never be forced into the hands of a hedge fund who will instantly turn around and start selling query data.
DNS could definitely be more secure, but the primary problem is the actors. Frankly, it seems to me much of the issue could be solved by the FCC treating DNS lookups the same as telephone records -- private to the subscriber, availble to third parties only upon court order.
In any case, you may care to explore setting up an experimental DoH server exclusively for Sonic subscribers, partly as a goodwill gesture, and partly to see what resources that would require.