Nope. You’ll only know how good is it when you run it on the actual hardware. Yeah you can install apps on Android emulator, but what makes or breaks custom ROM is driver support on actual hardware.

My bad, I was talking about custom tabs, which are provided by Chrome or Firefox.

WebView is a separate app, and you can switch between WebView and custom tabs somewhere in system settings.

The browser is what provides the WebView in the first place, so yes.

Missing a Raspberry PI 4 setup which hosts a print server, an RTP server with two surveillance webcams and no password, and also seeds a terabyte of torrents over the local flower shop’s unencrypted WiFi.