Hi, does anyone have any input/experience on this?

Would suggest using teflon tape on the threads. I've never had to add additional piping but seems straightforward to swap in an angled one as needed. If the old pipe is a bear to remove penetrating oil (or WD-40) and let it sit a bit. I think you'll love your new shower heads.

And there's tons of how-to videos on youtube,...

https://www.youtube.com/results?search_query=replace+shower+head+stem

The 2nd one appears to be a standard installation, where you just unscrew the head.

The left side brass colored shower pope may be a design that is similar to Kohler shower heads I recently installed. I had to screw a short pipe into the threaded fitting in the wall (it had an internal allen wrench fitting so it was easy to tighten). Once screwed in you had a a short brass pipe with two O-rings on it sticking out of the wall. I then slipped the shower fitting over the pipe and it was secured by the round plate with two screws into the tile. The two screws were covered by small decorative caps.

I would take a close look at the large square/rectangle piece at the top, and the round trim, to see if there is a set screw or other attachment to the wall, or a set screw that holds the piece to the pipe. I doubt that it screws on, since you would not be able to ensure it pointed in the right direction when it was tight. It probably has an O-ring under it.

I can't see the right side brass one well enough to guess how it might detach.

Bruce

Just be sure to not put pressure on the pipe that goes into wall that the shower head unit screws onto. Grab the pipe that goes into wall and hold that steady and only apply turning pressure to the old shower head you are removing. Same goes for screwing on the new one.

My sister put too much pressure, way to much pressure trying to get a new old shower head off and damaged the pipe that goes into wall.... : (