Is it weird in tournaments to walk out of your chair and watch other games?

Is it generally ok, rude, or distracting? I just wonder sometimes.

Pretty standard in my experience.

In longer games otb I need a break so when it's my opponent's move (and I am happy that my position isn't critical) I will often get up and walk around for a bit. Lots of people do it so it is probably considered normal.

Majority of tournament participants do that occasionally so it fairly normal. But of course it depends on the spesific time, like late in the game and little time remaining. 

You're allowed to unless otherwise told not too. You just can't tell the players anything. I do it all the time in OTB tourneys. It's quite fun, but it's mainly only in the top sections that do it, below certain levels almost never leave their tables.

It is allowed. I think there is an imaginary perimeter that you may not come too close.

For some, it's annoying. But, you have to put up with it.

It's hard for me to sit at the board for the full length of the game (although I've done it).  I think most feel the same way.  It's common to get up and walk around the playing hall on your opponent's time.  Might as well check on a few chess games while you're at it.

If I'm attending the tournament with club mates, then I always like to check on their games at least once during a round to see how they're doing.

I get up just to get the blood flowing, work out some of the tension. Usually right after making the first time control. I think it's normal. Everyone tends to do it, probably for the same reasons.

I don't see a problem with it, a mental break from anything is always a good way to look at something in a more refreshed mind.

Release nervous tension.