We recommend keeping the pony wall as you noted, privacy is key for the toilet area. 34" is a good amount of space for the toilet area.

The 78" vanity length is our preference but if you don't believe you need the storage and prefer that space to go to the toilet area, a 72" vanity will work as well.

What's the box in the corner by the tub? What's the opening to the left of the door?

You said you don't need much storage - do you have a nearby linen closet for towels, cleaning supplies, extra toilet paper? In your layout I don't even see a place to hang a hand towel by the sink or a bath towel near the shower.

How will you get behind the tub to clean, assuming it's free-standing as shown?

@AnnKH box in the corner by the tub is storage (open shelving and a drawer for a laundry bin at the bottom. Opening to the left of the door is a closet. Tub is freestanding.

@Sabrina Alfin Interiors good point on the door swing. So you would keep the 78" vanity or maybe leave room on either side of the vanity with a 72"? I like the window idea but we want to keep the window and like how the tub is positioned in front of the window. Open shelving/storage in the upper right corner.

Get a vanity with drawers and an open shelf on the bottom. That should give you plenty of space. The shower is too small, and you'll probably use that more than the tub. Give yourself more room and lose the linen cabinet.

The extra 6" at the vanity will be more useful than an extra 6" around the toilet. Most codes require no more than 2'-6" clear width at a toilet in this configuration.

It is a primary bath

Is the entrance from the bedroom?

What is to the left of the entry door?

Showing the whole of the area and surroundings van be quite helpful, along with complete dimensions