I'll second Buba68 that you're probably multiclassing too much, especially if you're not at all familiar with D&D. In D&D, unless you're doing certain specific multiclass combos at specific levels, you'll more likely than not make weaker characters by multiclassing. Single classes gain power exponentially, so a level 11 Cleric is vastly more powerful than a level 6 Cleric/5 Ranger.
I worry that you'll make these multiclassed characters and be severely underpowered for the encounters---especially in Act 2 or 3 of BG3---and as a result be more frustrated with the game. My advice is to play the game with singleclassed characters at least until level 5, and only then *consider* (not necessarily commit to) branching out to take maybe 1-3 levels in one additional class. This way, you'll at least have the basics of the game and the D&D/BG3 mechanics down by then.
And also as Buba68 said, subclasses (you choose them at class levels 1, 2, or 3 depending on the class) already serve the purpose of multiclassing in D&D. Shadowheart is by default a Trickery Cleric, which is a Cleric/Rogue multiclass.
Edit: While I was typing you posted this, which I mostly agree with.
U are right, there is probably too much multi-classing for most companions. I will lose a bit of power. Just 1 class or 2/3 dip max is probably a lot stronger. Multiclassing 6/3/3 or something is probably too much.
However.. i prefer options above optimising. So being a bit weaker overall, but having some more options seems like a good trade off. I do feel that the overlap is not that bad for my choices. Most use the same stats. The damage scaling may be the biggest issue.
If a character feels a bit too weak i can respec him anyway.
