I played it a bit yesterday, and answer to most of your questions are obvious right from the start.
- Happens everything on the world map or do you enter a combat screen when engaging an enemy?
Encounters are mostly random, and not visible before they happen. With few rare exceptions
- event points are visible on the map and 3d dungeon view, and they frequently include a battle
- I have found two stationary monster groups that are visible in the dungeon too
- the "nightmare" encounters are special in many ways
- about pacing:
1.) Is everything turn based (moving and combat)?
2.) Do you and the enemies walk around in real time but you enter turn based combat when you touch an enemy ( like the trails games but with grid movement)
3.) Is everything real time ( like legend of Grimrock, I have not played it but I saw the video )
Most of things are turn based. You move in square grid, battles will happen (or not) when you move to a new square. Battles are turn-based too, you have queue of characters and monsters based on initiative (AGI) and they will take turns. A bit similar to Trails combat (and many many other JRPGs), minus the random turn bonuses and s-breaks to take advantage of them.
Nightmares hunt you through the dungeon in realtime.
- Are there any survival mechanic outside of hitpoints? ( Like your chars have to eat or they have to treat illness or injuries other than just using a potion or spell )
Didn't notice any. Any debilitation from combat stays in combat and is cured after you win. Except for hp and sp, those have to be regenerated by consumables, healing spells, or automatic full restore by visiting a city.
- Are the world map and enemies generated randomly or is it always the same?
Map is always the same. Encounters are generated radomly from the fixed set of possible monsters for current area.
- How difficult is the game? I have much experiance with turn based JRPGs but not with dungeon crawlers.
The videos or screenshots in the shop often do not show much about actual gameplay for many games.
I am good in turn based games and real time with pause, but I am bad in action games. Moving and clicking on actions, items or abilities all the time like in Legend of Grimrock would be nothing for me.
I do not mind a complex class and skill system as long as it makes sense. So a fighter should have high strengh and a big sword and a white mage has high int and healing spells. Final fantasy II would be an example for a system that sound sound good in theory but it was the most unituitive BS you had to do to get a good char ( I mean FF2 for NES, not FF5 for SNES that has been called FF2 in the western world sometimes).
I have played too little to answer this reliably. On normal difficulty, I explored most of the first area (City streets) without too much grinding, killed the boss there (with some trouble, but on first attempt) and opened a second area (and my team got replaced by complete pushovers with no equipment so I got my ass handed to me, barely managed to escape from the first fight). I guess I'll have to go look for my original team before venturing there, but it was too late yesterday. The class system is not too complex. Stat growth seems to be determined by chosen class, no randomness. You have option to respec to another class and continue to gain power, similar to wizardry 7. Which likely means it will be hard to screw yourself permanently - even if you make bad choices, just delevel and try again.