I will preface this by saying that I have about 450 hours played in DRG :)
Complexity: I'd say "mid to low". Once you get used to the missions (knowing what to do), the complexity drops. This also applies to the biomes. Each biome has a "structure style". Even though each level is always randomly generated, you will start to get a feel for how the level will "flow" (best word I have in my head at the moment).
Stressful or anxiety inducing: There may be some frustration because you JUST. NEED. TO. GET/FIND. THAT. ONE. LITTLE. THING. but such instances are very very very rare. For 99.9% of the time, it's typical "do this, do that, complete these objectives, do that side thing, call for evac, GET TO DA CHOPPA". Celebrate with beers, repeat :)
That said, I play on Haz 3 (there are five difficulty levels) just to chill after work. If I want to play something more challenging with my friends, then we'll pop it on Haz 4 or 5 :)
Voice comms: Nope; not needed. You can press CTRL to ping stuff so most comms is done that way. Ping to mine something, "we should probably focus fire on this thing", or go to somewherer. Press V to "ROCK AND STONE" (most important button in the game imo). Anyway, no, voice comms is not needed. There is text chat so it's good practice to press "r" to tell others when you're ready for the mission to progress (or call for evac).
Playing with strangers: About 80% of my games are with strangers. It is really easy to host, and hop into games and the game is made in a way where voice comms (see point above) is not needed. We all know what we have to do, so it's nicely straightforward like that.
A++ can recommend.
We look forward to working with you on Hoxxes IV
ROCK AND STONE!
For consistent fun: Codenames, The Resistance, Secret Hitler
Recent board game which I really enjoyed: Takenoko. I loved the change in game phases.
Most chaotic fun I had years ago: Captain Sonar!