Delta Business seats

I'm off to Salt Lake City in April. Usually use miles to upgrade with VS and was planning a SFO or LAX UC flight with VS and then back to SLC with Delta.

However Delta Business fares look quite good at present £2400-2700. Has anyone flown this route recently?
Which route best? via MSP and SEA seem quickest at 13h+

Which plane 777 (herringbone seats, newer?)
767 (forward facing, are they better?) - some have winglets, are they newer planes?
Do Delta fly a 747 on any US routes?

Looks like I can still earn miles and tier points. Would I be able to use the LHR clubhouse?

Sorry for all the questions - I've always found US airlines grey and boring with surly CC but wondered if anyone would give this a try, at least I could save my miles for summer hols!

Thanks for the advice......

I can only answer the Clubhouse question.

If you take the MSP flight, no, as it leaves from T4 and the Clubhouse is in T3.

But if you take the SEA flight, yes, as that will leave from T3 when it launches in March. Delta's New York and Boston flights are also moving from T4 to T3 and all business class pax will be allowed into the CH.

I don't think DL use 747s on any of their US domestic routes apart from one Atlanta-LAX flight which is presumably a positioner for an LAX-Far East service.