The actual timings are in the FCIF\Announcment of the bid.
As pinseeker said, bid what you want. If you're close to the end of a seat lock and want to swap to the 777, request a waiver. Never get something if you don't ask for it.
Considering the size of the bid, if it was my call, I'd release every WB FO to bid the 777 if they wanted to.
For those who've never been here for a bid, people bid weird stuff and then change it for the final. Actually fitting their own name in at the relative Seniority level is apparently too hard.
Actually bit one of the buds when he input a practice bid at 100% to see if he could get that Capt seat and then, thought the final was a day later than it actually was.
So, bottom WB Capt for quite awhile. Which can suck, huge. Likely sucks way worse on the 75 though. Wouldn't think it would be that painful on the 777.