Here have utilized Digi USB to serial Edgeport devices for many years now. (1 USB to 8 serial). For single USB to serial always used smallest footprint device that I could fine.
For a bit there was an issue of cheap clones which did not work with Windows 10.
PC Touchscreen wise you can go to a mini TV Intel box which has the OS running on Emmc, VGA / HDMI ports, Gb NIC, wireless and built in bluetooth using less than 10 watts of power (and POE powered) and change over to embedded Windows. CPU is passively cooled in these micro pcs. You can velcro these pcs on the back of the touchscreen.
Intitally tested the Pipo mini PC and recently tested the Beelink BT3 Pro. Needing an old style serial port and VGA went to using a Qotom pc for a PFSense firewall.
The Qotom PC is larger than the BeeLink BT3 Pro.
New generation touchscreens are 16:9, multitouch and utilize much less power than older ones. Might be able to use one POE powered connection for the PC and touchscreen now a days.
BTW here purchased openframe very thin multitouch screens with a very small hardware connection section in the middle of the back of the monitor. It was just about a flush mount to the wall. Finished it with a custom wooden frame. Looks a bit nicer than DIN mounting a screen to the wall which I have done with a few LCD TVs.
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