I have an offer from company A, I also have onsites coming next week for company B. B is more prestigious than A. B is also known for having a long feedback time and team matching. I can't just wait until B gives an offer/rejection because it might take too long and A could expire. Would it be wrong if I take the offer at A and then jump to B if I get their offer? Or how should I handle this? I would prefer to work at B but I also don't want to end up unemployed.
You have to look after yourself first. Just don't make a habit of doing this.
If company A is small and/or tier 3 no problem. Else weigh the risks
How much time can you ask for from A? Probably better not to renege at all IMO.
I was in the same situation. Accept A and if B works out, make the switch only if you are okay with what might be the worst case scenario: getting blacklisted forever at company A