Thanks for all the responses.

booked on United.
flight was a couple of weeks ago.
LH didn’t explain options. There were 5 of us. Not sure how many were overbooked but the upgrade fee of $400 each was acceptable to the girlfriend and the kids. Mia to Frankfurt and we got seats on upper deck Biz class so wasn’t too bad. Everyone was happy.
I’m not sure how LH charged us in terms of upgrade terminology.
I guess it’s doubtful to get extra miles especially as the fee wasn’t too much for a Decent flight. Thought I’d ask.

thamsk for all the helpful responses. Will be aware in the future oif other options.
cheers