Oceanias and Terras, at least right now, seem to always have over 4 pressure or under 0.2 pressure with their atmospheres. They're often above 10. Is that normal, or is it a bug? I can't imagine how a planet would gather that much without being a failed gas giant...
Just found a planet with 1715 atmospheres. I think SE is toying with me...
Tips for finding Earth-Like planets: Look for F, G, or K Class stars. M class habitables will almost always be tidelocked. Oceanias can, of course, also be habitable, they just have tiny amounts of land.
Well, Venus has 90 bar without being a failed gas giant and is really warm, so we know Earth-sized objects can have huge atmospheres without being failed gas giants. That said, the atmosphere's aren't as well simulated as many other things in the current version and will probably improve in the future.
It's worth noting that Venus has pressure high enough that the CO2 in the lower part of the atmosphere is probably a supercritical fluid. I've seen worlds with "life" in SpaceEngine that, strictly speaking, should be coated in high pressure ice phases or supercritical oceans of oxygen or whatnot.
The atmospheres seem to be generated almost purely at random, as I would expect that if they correlated at all with the presence of life, at the very least it would have to be 'exotic' life for most of the atmospheric pressures you run into. It's not enough to have the right temperature - the properties of water and oxygen and CO2 are going to change at different pressures as well.
Then again, playing Devils Advocate against myself, maybe we can assume that the life that is present is at high levels in the atmosphere.