The shiplap ship has sailed hopefully sunk. I think the issues with the drywall could be the fake beams causing the issue.

Shiplap doesn't work with your existing furnishings. Hire someone to figure out the cracking.

To me the beams don't look to be a feature worth emphasizing in this room. There is no guarantee that stripping and staining them would give you the result you want, either. If you decide to go down that road, strip a small spot that is in a less visible location to see what's under the paint. Unless you installed them years ago yourself you have no idea what it is.

I recently moved from a home I lived in for 20 years and also remodeled from the slab up. I had cracks appear around the perimeter of the rooms where the walls meet the ceiling. I personally think some cracks in sheetrock are just going to be there, given time. A compounding factor in my case was the home was within sixty miles of the Gulf of Mexico and I had hurricanes. I didn't have any significant specific damage but the winds probably put additional stresses on the house. That aside, I'm also a wood worker and anyone who works with wood, for framing, musical instruments, or furniture, knows that wood moves with changing humidity. Unfortunately, sheetrock tends to crack when it moves....especially at the joints. Why have we no flexible sheetrock finishing materials???????

There is a product called retique it that you can apply and then stain. With the right electic rugs art decor drapes it coukd look good