One thing I like about magic in games is it's tendency to break up the realistic mechanics. When everything else is based on reality, magic sets the designer free to come up with something new and different.

It's a double edged sword though, as a realistic setting, the player can infer what something does by what it would do in the real world. An anti-tank gun is going to be good against tanks, a machine gun is going against people, and so on.

Anyway, depending on the game, but I prefer hidden information, but low randomness. Position units for ambushes and such, submarine warfare, having to properly scout and use recon units, etc. That said, one of my favorite tabletop games of the past was Through The Desert, which had zero randomness and full information. Games that have a high random factor can irritate me, as I feel like I'm too much at the mercy of the random number generator.

If you go with the hidden approach, just make sure that the player can estimate what he is dealing with.

For example if you have a small goblin, the player will expect it to have a very low health amount, therefore if you give the goblin a ridiculous amount of health the player will get annoyed. If you create a new race or type of goblin that you want it to be strong, maybe change the picture to a slightly different goblin, give him armor or whatever, and maybe hint the player about the new goblin race/type which is known to be much more sturdy than the regular ones, this way the player can hypothesize a health amount for that goblin and not get annoyed when it takes 3 hits to take it down instead of 1.

In general what I see is that people tend to get overwhelmed by too much information, and just start ignoring everything and try which moves work best, then spam those moves. With too little information the same happens.

One of the types of information you can hide:

• enemy hp numbers: have a bar but not numbers, That way players have to estimate damage a bit more.
• As other have said, fog of war can be useful, or you could have waves of enemies, which would make it so players would have to prepare for the unknown
• I think that in general, having set types of enemies can be useful for prediction consistency, but keep most of your non-sharing to do with enemies. On the flipside, make sure to provide the player with all of their own character information. It's frustrating to not know your own capabilities, but interesting to have to figure out the opponents, though that can range from learning their 2 attacks and health to fifuring out how to get close enough without being destroyed.
  
  Good luck!