When it was free on steam it was a much more generic ww2 game and I believe the factions didn’t even have the fictional names they have now.
Now the devs have made a point to say it is not a simulator for any of the world wars though inspiration has been drawn from an amalgamation of 20th century warfare.
It’s completely fictional but the other reply is accurate in that it’s more WWI or interwar period themed.
I believe SOMA is less horror-y and generally more approachable than the other frictional games. It may be because it’s a scifi story, like the other games you mentioned enjoying.
I used to hate horror games, but I realized I actually just hated bad horror games. SOMA is a good horror game. It has a compelling story, fantastic atmosphere and sound design, and the frictional games devs are great at balancing the suspenseful moments with more relaxed thoughtful moments. All of this makes getting through a stressful or scary bit of the game more worthwhile.
Like Ashtear said, the safe mode prevents the monsters in the few areas they patrol from ‘getting’ you, which I would say somewhat gets rid of some of the suspense. However, after you’ve been caught once and have to reload a checkpoint, they just become an annoyance so I wouldn’t blame anyone for turning safe mode on.
Their newest game is going to be on a custom engine. As for the games still being updated or about to release I think they said would be very expensive to rebuild in a new engine at this point.