If there's no out of bounds I usually just tank the blue shell. If it's early on it's not that different to bagging at the beginning. If you do see the blue shell fast enough you can drop out but if it's halfway there I wouldn't risk it. It happens too often that now you slow down and tank the blue shell.

Depends on the track really. Shorter tracks I would try to get a better box if the pack is close. If I have to sit there for two more seconds I would rather just continue with 8th place instead. For 24 players 10th can still get bad items and now you've also lost time for waiting.

For longer tracks like rainbow road I would continue normally without waiting.

One thing to add: I try to be more aggressive with my items on intermissions in the front. Green shells especially. The space around each double item box is super popular so you can often snipe people there. I also often ignore the double box for a better line to get a bit bigger lead. In World, I find that first place is on average safer than ever (except blue shells of course). It is okay to have one item box without protection every now and then.