Which touch screen displays?

[TheOldPresbyope]

Sorry I was not clear. Yes, the touch screen that attaches to the rpi.

Thanks for the great info, helps a lot. :-)

I looked at the photos. So the RPI will mount on the back of
the official touch screen? No issues with the DAC hat on it?

I have not checked yet. I’m using rpi4, not sure if it work with
the rpi4 connection wise?

Yes, the RPi mounts on the back unless you cobble together some other arrangement (which might require a longer DSI flat cable). This doesn't interfere with adding an I2S DAC HAT on top of the RPi. (E.g., from front to back the full stack is the screen, then the screen control board, then the RPi, then the DAC.)

The Touchscreen display should work fine with an RPi4B ... BUT ... notice that there are two ways to feed +5V to the screen. 

• You can use the included jumper wires to go between +5V and GND pins on the RPi and the related pins on the screen's control board. No problem here. 
  
• On the other hand you may need to keep the GPIO clear for a DAC HAT and instead connect power to the screen via the micro-USB connector on the control board. The RPi4B has a USB-C connector, not micro-USB so a simple "splitter" cable will not suffice without an additional connector adapter somewhere. Of course, you could also use separate power supplies but that seems like overkill to me.
  

I don't think it matters which method you choose to power the screen--I've used it both ways---just be aware that choices have consequences. 

Recently, I bought a SmartPi Touch 2 case to house the screen and an RPi3B+, along with the optional, extra deep back to accommodate an I2S DAC. I did this after seeing a post from new_bloke and exchanging PMs with him. I'm quite happy with this case. Right now I'm using it with a USB DAC. At some point I'll want to modify the back as new_bloke did to accommodate RCA connectors for an I2S DAC HAT so I can have a neat finished appearance.

Why did I decide to use an RPi3B+ here when I have RPi4Bs in hand too?

1. The RPi3B+ generates less heat so I may be able to do without active cooling in this little box. I still may end up trying to use the fan which came with the case (which will require some hackery with the deep back) depending on what kind of temperatures I reach in long-term usage in the summer.
   
2. With everything stacked in this case, the uSD card is impossible to reach without partial disassembly. The RPi3B+ can boot moOde from an easily accessible USB thumb drive. The RPi4B cannot (at least not yet). I remember seeing somewhere long ago an extension cable for uSD but it would be awkward to fit it in and I'm not sure how it would affect the performance of the RPi.
   

Regards,
Kent