I just visited some web galleries of bathroom remodelers in the US, and it looks uncommon to have external shower fixtures. They tend to bury as much of the fixture as possible in the wall. From the photos, I don’t get the impression they are using thermostatic mixing valves. But it’s hard to tell. Can anyone confirm or deny?
I think I might favor external fixtures because they tend to be much cheaper and also more easily servicable.
Cost is the limiter:
https://sanitary.nyc/thermostatic-valve-vs-pressure-balance-valve-whats-the-difference-and-what-are-the-pros-and-cons-of-each/
"Cons
By far, the biggest con to installing a thermostatic shower valve is the cost. These valves tend to be at least twice as expensive, if not many times more, as pressure-balance valves.
Another disadvantage is the trim that accompanies this type of valve because it has two handles. These can be trickier to install with simple plumbing upgrades because they use a wall-mounted plate behind the handles. They tend to come in contemporary designs, although it is possible to find models that work with more traditional bathroom decor."
The thermostatic mixers can get as cheap as €25. Though I think the cheap ones have a degree of slippage, whereby mid-shower I have to increase temp. I don’t know if that’s because it lost track of my setting, or if I adjusted to the temp physiologically and need hotter water to psychologically feel the same level of heat.
What kind of bothers me about the pressure balance design is you cannot tell from the pics if it’s really pressure balanced. I think the one handle style goes back decades, and originally did not maintain a balance. You have a joystick of sorts but if the pressure on one pipe changes you don’t know if it internally balances to maintain the ratio. So you have to read the product description and trust it.