Regarding United you will only have a decent product on the 777-300 specifically which is generally one flight a day and is often a redeye- and from what I’ve seen may actually only be going to SFO right now and not LA. Their 777-200 still sports a pathetic 2-4-2 arrangement (albeit lie-flat) in “domestic first.”

I used to fly this route a lot and would almost always fly Hawaiian which is a decent product for only a 5ish hour flight. But yeah don’t be expecting international food/service/lounges (on any domestic US route). US airlines do not provide lounge access for domestic flights, even first (except for HA departing HNL and again it’s very basic).