It's not a great spot with the Q9s, but that opponent was a loose Brazil reg; those players can absolutely find 4bet bluffs with Ax. They can easily overdo it because there are many more combos of Ax that don't want to flat a 3bet than there is KK+. I don't expect to see AQ or AK or even JJ for the sizing they chose. I feel confident enough in my post-flop skills and hand reading to make those sort of flats vs those sort of opponents. Assuming nobody can 4bet bluff in a $5 tourney unless they are a whale is a bad assumption IMO. I see more crazy preflop stuff from "regs' in lower-stakes tourneys than I do in higher stakes. Mostly because a lot of players at the lower stakes have less solid fundamentals and are just "trying stuff" or trying to outplay people too much.

It all depends on the exact spot, do you have a more specific example? There are some spots where open jamming 20bbs can be the right move, but it is usually only for specific ICM spots. For chipEV, there are almost no spots where I want to open jam 20bbs. SB vs BB is the only spot where it makes any sense to have an open jam 20bb range.

Like 20 bbs BTN or CO, I usually just rip small pairs and sometimes QJ KJs type hands, pre-final table.