I have slept with the top down, because I was curious, but I don’t think sitting at the table would be too comfortable with the top down. We’ve been in decent wind with the top up with no concerns.
Our 5yo uses the bunk every time we camp, but I think the max weight is 140lbs(?). It’s basically a cot, so it’s as comfortable as any cot, I guess. I’m a bit north of 140, so I haven’t tried it personally. The other kid bunk holds extra jackets, blankets, and other soft goods up out of the way, it’s handy.