Random but scraping the popcorn ceiling is an easy but messy diy, will make the space look much crisper & cleaner (dep on the age of your house you may need to test for abestos, but its simple enough to do that just google how-tos)

A built in vanity with side filler strips and a wall to wall top would be sleek and easy to clean. Vanities with legs and gaps make it much harder to keep walls and floors free of dust and drips around them. A medicine cabinet adds lots of storage.

With a 29.5-inch opening, I would usually choose between two clean approaches instead of trying to split the difference awkwardly.

Option 1 is a 28-inch vanity cabinet with side fillers and a wall-to-wall custom top. That tends to look the most built-in and solves the countertop gap issue cleanly.

Option 2 is a deliberately smaller freestanding or floating vanity, but only if you treat the side gaps as intentional negative space and finish the back wall accordingly.

From a production and QC perspective, the most important detail is not only cabinet width, but how the top overhang, side fillers, plumbing location, and mirror or medicine-cabinet alignment all work together. In a small half bath, a well-proportioned built-in look usually feels calmer than leaving random side gaps.

Buy a 24" floating vanity, and DO not tile the back wall : )

All it will do is call attention to the clipped ceiling.

I would do the 28" with the small fillers and a custom counter to fit wallto wall.No fancy shaped mirror just one wall to wall and a simple bath bar for lighting

do custom floating vanity wall to wall. we have an angled wall above vanity in a bathroom. we had mirror custom cut to fit full wall with bar light on ceiling at top

I would either get a custom fitted vanity or do the freestanding 24inch. The 28inch is just inviting you to drop your toothbrush in the gap..

How to Design a Luxury Bathroom?

Buy a vanity that fits in the space and use filler strips but have a custom sized top made the fits the exact space. Another option is to do something completely custom for the space. See below.

OR,......select a smaller vanity that allows enough room to get a paint roller between the vanity and the wall. Don't kid yourself, you'll need to paint eventually.