You can get a fine shower from a handheld. If I'm installing just one head in a shower, I recommend the user go with a handheld. They're more versatile, and there is no performance penalty. Understand that many manufacturers use the same shower head for fixed and handheld applications. Same head, just a different presentation. Example, here's the Grohe Relaxa Top4, which is what I have in my shower: Fixed: Handheld: I'll agree with raehelen too regarding the bench. I'll encourage you to eliminate the built-in bench and go with a movable wood stool or bench. Again, more versatile. And more comfortable to sit on. Two heads in a 65" shower is not excessive. Regarding the rainhead and pressure. You are correct, many people who use a rainhead as a daily shower head to shower an shampoo do indeed get frustrated with it. It's not really intended to function that way. But those who use a rainhead for the "rainhead experience", they love the rainhead. If your two heads will be used for functional showering, I'd recommend a fixed head on one wall and a handheld on the other wall. Make the handheld hose long enough so it can be used to wash down the walls. I probably install more Grohe than anything else. When you do change shower heads, there sometimes is a transition when going from what you're used to to what you now have. The new head isn't worse. It's simply different. For your plumbing layout, consider having the supply valve(s) located just inside the shower so you can turn the water on without having to step into the shower. The idea is to eliminate getting hit with a cold spray when you turn the shower on.

I have a neo angle shower, and we placed the shower heads centered on the long walls opposite the door. The valve and diverter are directly beneath the stanadrd shower head. The other shower head is a handheld on a slide bar, and we have a rainhead in the ceiling. We considered putting the valve on the short wall inside the door but ultimately decided against it, becasue we wanted to keep all the plumbing on the far walls. If we ever decide to glass in the entire shower or the next owner wants to put in a tub, it will be much easier.

A 2/3rds-height toilet wall would contain pretty much all of the water. You could go 3/4 for more protection and a bit more shower privacy. My shower is about the same size and the wall opposite the shower head doesn't see much water up high. Rainheads are a nice for what they are. I have one as a secondary head and we both like it. But as a primary shower head, no I don't recommend them for that. For large showers like yours, I do recommend a handheld somewhere in there with a long hose. Handheld heads offer the same spray strength and patterns as fixed heads. Having one of your heads on a long hose allows you to easily rinse down all corners of the shower when cleaning. Handhelds can be on a sliding bar or on fixed brackets. Consider mounting the shower valve by the shower entry. That way the shower can be turned on without having to step deep into the shower. Depending on where you locate the shower head that is closer to the door? If this will be a doorless entry consider tiling the floor outside the shower entry. The bathroom floor between the shower and the vanity might see some droplets.

It's not up to the other trades to notice this, and it is not up to the homeowner. It's also not the inspector's responsibility. No, it is not functional if you intend to use it as a tub and not just an oversized shower pan, as olychick pointed out. What is that black line and bump-out in the wall on the plan at the drain end? This doesn't make sense to me: "As it is now, I have to walk into the shower as the door is on the same side as the shower head" You would want the door to open on the valve side, so you wouldn't have to walk around the fixed panel. Maybe they did it to fix that problem, since the toilet would be in way of the door opening if the door were on the other end.