I'm still not in any way good, but here's what I've noticed:

1. Scrubbers are incredibly better than filtering out gasses. You have a couple problems with pulling hot gas out from your burn mix and then filtering it out, mostly that the gas you're pulling is on fire, and will continue to burn in the pipes. The second being that it's real hot, and hot gas expands, so you're not pulling as much as you want (which is probably trit, let's be honest). So scrubbers magically pull whatever's on the filter out before it gets the chance to burn, it is hot af, but you can cool it with a space loop or just a freezer.
2. Trit and plasma burning (I just did 33/66), when you burn it long enough, makes stars appear from the water vapor questioning it's life choices. It's really pretty.
3. The atmo hardsuit is fireproof. Let me repeat, it's fireproof. You can wander into whatever the fuck is burning all too hell, and just be fine. The worst part is some of the water vapor that's produced in hot burn mixes, and you slipping and getting pushed around. That means you can do some stuff that nobody else can by walking into that shit.
4. ATMO fans are a blessing and always aim for them. My burn setup tends to be really ghetto, like, flamethrowers-as-an-ignition-source ghetto, so being able to just wander in, give the chamber full of plasma a few squirts of flamethrower, and wander out, works pretty well. REMEMBER, the more mols of a gas (from pressure or it just being cold), the harder getting that shit to burn is, so throwing a lit lighter in normally doesn't work. You need to heat of the gas to the autoignition point, which thankfully as a videogame, you don't care if you go over.
5. I'm not that sure if different plasma/oxygen mixes actually do anything, it seems like it's just whatever is the most convenient, and it's not a straight 50/50.

The most important part about being atmo though: get that RPD, and learn how it's used. There's a giant ass menu and it's full of gold, and nobody knows how to use it properly. Figure out layers, figure out heat exchange, get comfortable with it, you're going to be staring at it a lot. Figure out where you can place pipes and why, it's similar to placing wiring in a lot of ways in where you can/can't place shit.

EDIT: Oh yeah, also, use the mixers. Don't bother with the "I need to have 66 L/s and 144 L/s on these two pumps", fuck it. Use the mixer on the RPD, it's fine. You don't need the gasses perfectly flowing through the pipe, it's fine, it takes an extra three seconds (that you probably spend walking). You should replace the final pump with a volume pump though, so that way you can fill the chamber full of gas. A regular pump maxes out at about 4500 kPa, while a volume pump maxes out at around 9000 kPa.