Looks good. If I was you I’d tape off the footprint of a 75 gallon on the floor. I recently did my rock work and I actually taped off my footprint but 2” shorter on each side so that my rock work would leave space for cleaning and powerhead placement. This way you get an idea of the space you have to work with.
Definitely make sure there’s space between rock and glass as mentioned above. Makes cleaning easy. Looks like a nice setup. I used a similar setup for my tank and it worked out pretty well so far. Just remember to put the rocks in before you add sand so no fish you get later on can undermine and knock things over.
I know corals will change it up some, but height level looks like a straight line all the way across. You could maybe put a small arch type above from the center to halfway over the left hole. That would give you the look of low, tall, middle heights to break it up. Like the look of it.