I don't think there is another thread on this.
I have been playing for 5 years. I have been sitting and playing mostly, except for a few gigs playing easy material.

I want to start playing standing up, but I can't seem to relax my right hand, especially when I'm tremolopicking. I can relax if I'm sitting down.

Is it normal to have your wrist angled?
What height is best to set your strap at?
Any tips?

For wrist angle use what evers comfortable. Just practice playing song you can play really well sitting down and just practice them standing up. As far as strap It all up to you I personally play my guitar right up to me cuz I find it the easiest to play technical stuff but I have friends that play their guitar down by there knees and they play flawlessly so all you man

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I'm going to respond to this just because I went through a two year phase of trying to pick correctly.

1. Yeah, stay relaxed.
2. Your fingers should not curl up, let them dangle. You don't need to plant them like rocks, but let them rest for better support.
3. Pick with your wrist, please. Look in the mirror to make sure you're not using much thumb.
4. Move your whole arm in a comfortable fixed position when moving up and down the strings. Find string skipping exercises as well.
5. The angle: don't let it get too flat or too angled. Yngwie uses a pretty good but extreme angle. Someone like Alexi Laiho has a less extreme angle, but uses planting well (I'm just throwing names out there).
6. As you get down to the low E you may have to support your hand with only your pinky or use some other support. Find something easy and comfortable.
7. FUCKING SPEED BURSTS: they will make everything ten times easier. Do them fast but in small bursts, and don't strain.
8. Pick near the mid pick up, slightly above or below. I've seen both work fine.
9. When moving across strings towards the high e, I move my picking area to above the mid pick up. When coming down I move just below it. This is better than just staying in a straight line.
10. My thumb and index finger form a pretty big cave when I look down at my picking hand. This seems like a sign of easy and loose form. Don't scrunch up.

If that was too little or too much information, just tell me. I just remember my frustration of not being able to achieve good form, so I can sympathize easily. And I've been playing for almost seven years, and currently I'm majoring in classical guitar in college (while still fuckin' jamming the shit out of my electric of course) so you can trust most of what I say.

I hope this helps.

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how do you anchor your hand, or is it just loose?

i'm wondering if when you're sitting, your forearm is anchoring and when you stand your arm just hangs...

i find with metal there are so many palm mutes, it's easiest just to anchor my hand across the bridge, leaving the pinky side of my palm on or just above the strings. just watch any of your fave players on youtube and you'll see that their hands stay put in that area for the most part. you don't need to be waving your hand all around like folk acoustic strumming. just park the hand and flick that wrist!