We've been on 25+ trips with Cunard, almost all QG. We've crossed the Pond at least a dozen times.
Our son and DiL just returned a couple of weeks ago from a TA roundtrip in Club, deck 12. They thoroughly enjoyed it, even although our son had travelled QG several times.
Hard to say what we wish we knew before first sailing, because we had done our research.
There is a daily auto tip charge (now known as Hotel Charge) we do not remove it, but tip a little extra every evening if the service is good. It's never been bad!
Get to know the staff, especially your waiters and your sommelier. Some people think they're servants. They're not. They are just people with a different job.
The Atlantic is the most unpredictable ocean on the planet. We've sat outside in November, but had fog in summer. Some kind of waterproof/windproof clothing might be useful. However, your skin is waterproof! The pool on Deck 12 (indoor) was closed recently, but usually they will be open.
For the last 12 years, we've been using: https://www.tmrchauffeurs.co.uk/
They have luxurious Merc S-Class cars. Soton - London is about £250.
Very reliable and will wait if there's a delay.
Good luck, but just be prepared to keep chucking hard earned cash at Cunard from now on. We all do it since we've become hooked.
Stewart