-health and mana dont regen as fast as in Skyrim. Thats great for me, I want all those potions matter.
Because of the "fever" constraints, I've found that food is probably at least as important as potions. In fact, I get a bit paranoid about using any potions because of the fever.
-Combat pace is perfect on Adept. I'll probably play on Expert to make it abit more challenging.
I'm sure you will find it challenging (personally, I find it more difficult than Nehrim). Just wait till you walk around the side of a hill at level 3 and run into a few Arps!
Now I'll say one that I dont. Monsters aggro radius looks very small. I constantly saw enemies dont see a player when he stays just few meters from them.
Keep in mind that when you watch those streams, you likely don't know the player's level, skills, talents, and magic equipment, so what might seem easy for one player might not work so well for a differently equipped player. So don't judge it just by watching streams until you've tried it yourself. (I don't read more than a few words in German, but I'm having a blast playing it just going around at random, just clicking on every dialog choice when I rarely encounter a friendly NPC -- I even accidentally completed one quest like that!)
Yes, sometimes you can sneak near or past enemies. Don't count on it. Likewise, they can sneak up on you, especially in the tall grass. You won't know there is a giant spider behind you, and the next thing you see is the loading screen after your death!
Up through level 3, I've been killed by a wolf, a spider, a team of giant rats (or whatever they call them), an Arp, a troll, a skeleton, and an archer bandit from across a river that I didn't know was there till the arrows hit me, and many many times I've been taken down to just a couple of health points remaining.