If you have tile on the wall adjoining the tub select a caulk that matches the color of the grout.
How to hide a huge gap between tile and wall.
With the uneven look you may need to shape the molding to fit.
If your gap is smaller than 1 8 inch in width use regular caulk.
This will give you say a perfect 3 8 caulk line with an irregular wall to counter gap.
The steel studs are perfectly straight.
The only thing to cover the gap would be to use 1 4 round molding.
Great remodelers and builders consider using galvanized steel studs in locations where there will be tile.
Lay painter s tape along the edge of the countertop and the wall just above the gap to keep caulk off these surfaces.
Tool the caulk by drawing your finger along it to form a concave surface.
Fill gaps larger than 1 8 inch.
Choose a color that matches the countertop and spread a thin continuous bead with no voids.
Your tile person will take the largest gap and run a tape line using that as the thickness or the caulk.
The line will continue maintaining caulk gap regardless of the gap of the wall to counter.
If installed plumb and square the finished tile work looks amazing.