One of the core purposes of Tor Browser is to reduce browser-fingerprint uniqueness. I can’t say whether the Apple version requires compromises on that, but it’d be alarming if TB on iOS failed to at least mask the Apple factor. Worth noting that adding extensions to Tor Browser can compromise the anti-browserprinting effect.
Tor Browser is not just for onion services. You should be able to reach clearnet sites using exit nodes and that should be automatic.
I would not worry about adding congestion to the Tor network. The Tor community relies on cover traffic to some extent.