Geromino: Err no, the main character is not at the front of the party in BG1+2, unless you tell them program to do exactly that.
You can control who the enemies attack much better than in BG3. Its almost always just whoever is closest.
I have played BG1+2 douzens of times, usually on a Sorcerer. The enemies never targeted me. (*)
They do that in that EE addon, uh Black Pitts. But not in the main game.
And yes if you go into the wrong areas you WILL die. Thats by the way true for BG3, too. Thats why the game gives you directions where to go. Ignore at your own peril.
That said yes there is a way to reveal Improved Invisibility even at level 1, though it doesnt matter. The enemies that use Improved Invisibility are not meant to be faced at level 1 and will wipe the floor with you either way, even if you manage to dispel their Invisibility.
(*) Okay admittedly the original BG1 didnt have Sorcerer as class, so that was a mage back then. Sorcerer in BG1 is a bit boring anyway, since it takes so long until they get a decent number of spells.
* The main character is at the front of the party if you don't go out of your way to change that. Plus, there's no guarantee that you'll have that many companions early, since some of the early ones are listed as Evil if you check their character sheets.
* Someone new to the game won't necessarily know that enemies attack the closest character.
* I believe that invisible casting enemy was in a place I was supposed to go, in a sidequest.
* Would a newbie know how to remove Improved Invisibility and expect it to be used enough to invest in that capability?
One other thing I remember: If the enemy uses spells such as Entangle or Hold Person, and you then kill the enemy, the spell will still remain in effect, forcing you to wait before you can continue, and that's annoying.
(Some of these problems go away with familiarity with the game, but that doesn't help a first time player, and other probelms are still present.)