How to Vecna?

This is coming from a cynicist, so disregard or take it with a grain of salt. There's no point in being a perfect manager of your spells' timers. You just use them when they're available and fit your situation. And you can't actually see your spell menu while you're blinded, just a tip. Wouldn't be surprised if selecting them slowed you down a bit either.

The orb is used to counter magic items' effects and to find survivors across the map, so either use it in chase or to find distant survivors. And there's a small learning curve to how the orb actually travels; in the beginning I often aimed too high or too low.

The skeletons usually never get hits unless you spawn them point-blank on survivors, or if you manipulate the elevation at which you launch them (because that will take away the "just crouch" counterplay)(there's also an add-on that does this). You could also try to snipe with them, but that's just as dice-rolly.

The fly is used mostly for mobility. It can also be used as anti-loop or to cut people off, but I wouldn't put too much stock into that. It insta-cancels when you vault a pallet/window with it, but the survivors will either get to go through your body for free, or just use the really long cooldown you're stuck in to get another go-around at the loop anyway. And to me, it's not as much distance gained as it "feels like," with the audio/visual effects.

The mage hand is probably the most overrated of all. It's best to use the Haste add-on with it, because otherwise you don't even catch back up to the survivor at the loop when you use it; it's like you simply broke even on distance to them. If the survivor has magic boots (which gives THEM Haste when you use mage hand), definitely use the orb first, or else there's no point in using the hand. You ideally want to use mage hand to pick the pallet back up as a survivor is dropping it, so that they're recovering from the animation rather than full running at the start. But even then, whether you get caught on the lingering pallet hitbox or not, you usually don't get the survivor, and if anything you just allowed them to re-use that pallet, literally just wasting your time.

You can try whatever add-ons or perks, but it really doesn't make much a difference, except the pink add-on that makes hand destroy pallets, or the fly add-ons which makes fly feel much less janky. Or his trapped chest (or mimic) add-ons, because occasionally someone will miss a skill check and take damage.

But genuinely I don't know how people catch survivors with Vecna. He's all style, no substance. I'd almost recommend not learning him, because for me, playing him has felt like a big waste of time.