I use firefox on desktop. But on mobile one major blocker for me is that Google assistant does not work with firefox browser on android.
If I choose Voice and Assist app as Firefox instead of Google then active edge, Ok Google does not work. May be I could just try setting browser app to firefox.
Let me give this combination a try for a few days. Browser is firefox and assist app is google which as you say still renders some links in android webview.
"Assist app" settings determines which app can respond to assistant invocations (ok google, long press home, squeezing the phone...) and grants special assistant privileges to app.
Default browser is another setting :)