About the bleach, wouldn’t it just evaporates into the air

Nope, bleach is Sodium hypochlorite, if left to dry only the water it's diluted in will evaporate leaving behind bleach crystals. Over time it will decompose into table salt. That doesn't sound the best for the humidifier, but it won't be a danger to the air.

Well if you have ever been to a pool you are breathing in a pretty heavy dose of chloramine and depending on where you live there is likely chlorine in your tap water. I've even had to wash my veggies and fruits in bleach water because of parasites. It's not exactly healthy for you but it's not exactly harmful as long as you don't do anything stupid. It's a cleaning agent.

I'm using about a teaspoon for a gallon of water and actually settled on using a pre-diluted mixture in a spray bottle and just spray some in when I see it getting moldy again. Which is to say I also only do it like once a month to 2 weeks and try to do it before leaving the room or house for a bit to let it run without me immediately breathing in.

The other recommendation would be hydrogen peroxide since it breaks down a lot faster into just water anyways but it's slightly less effective and less easy to just have on hand.

Salt seems like a terrible idea. I have super duper soft water with nothing in it but some basic calcium.... Calcium powder is always settled all around my humidifier. And nearby glass surfaces. It will carry some salt with it, guaranteed. Plus I see it clogging important mechanisms or pores.

I use a little splash of vinegar. Keeps it nice and clean without the whole chlorine gas part.

(I don't know if bleach produces chlorine gas. Talking out my ass on that part)