If you want the wall to be perfectly straight, you can’t avoid leveling it. You can either use battens adjusted to the wall’s unevenness and then install drywall over them, or have it plastered and give the plasterer clear instructions on how straight you want it.
If the beam only protrudes at the top and isn’t too disruptive, I think leaving it visible can be quite charming. Especially in older buildings, this can look really nice if you highlight it intentionally. Sanding, oiling, maybe adding indirect lighting—there are many possibilities.
It basically depends on whether you want it technically “fixed” or if you’re open to making it a design feature.
If the beam only protrudes at the top and isn’t too disruptive, I think leaving it visible can be quite charming. Especially in older buildings, this can look really nice if you highlight it intentionally. Sanding, oiling, maybe adding indirect lighting—there are many possibilities.
It basically depends on whether you want it technically “fixed” or if you’re open to making it a design feature.