There is a lot of things to unpack here. Be aware that you need to have an understanding of D&D 3.0 or 3.5 (or Pathfinder, obviously) to have a chance of *not* breaking your teeth at your first attempts at this game. If you don't then the difficulty is going to be steeper than that of the Dwarf Fortress back in the day. The game is designed in a very old-school way, and I mean it; without a guide you will miss several things, you will lose a lot and there will be plenty of choices you will regret, gameplay-wise (and that is both fine and a welcome, although hard to bear, change from contemporary games). If you're fine with both (or feeling nostalgic for original Baldur's Gate and the like) you're going to have a truly wonderful time: The story might not really be top-of-the-line, the characters are not the best written companions to find in video games' world, and the gameplay has its share of bugs; but somehow all of it combined works wonders and will suck you in for hours withound end. Plus, if you've ever been charmed by Fearun's wonders (either dealing with Bhaal's spawns or saving Ten Tows) you'll feel right at home. The game's world has amazing reactivity to player character and actions, especially in chapters 1-4 (5 and 6 look and feel rushed), to the point you will want to create different characters just to see how different dialouges and quests play out. On top of that mythic paths add a significant amount of replayability to already long game - I had 200+ hours sunk into it when I managed to finish the game for the first time. The RTS-esque "crusade mode" is boring, tedious and unrewarding; I found it to be more of a nuisance than a benefit to the game. TL;DR Tedious, glitchy and difficult game, but very rewarding - especially for anyone longing for "classic RPGs" like original Baldur's Gate, Icewind Dale or Pillars of Eternity.
