Heya John
A few points as im falling asleep
Idea type of conduit for your sockets is oval conduit in 20mm, this is almost rectangular, but its well oval
You would be looking at getting 2x 2.5mm cables in this most, for your rings etc.
Small metal protectors e.g. plates for protecting cables in notches don't need to be earthed.
I wouldn’t suggest using steel conduit unless you can thread it properly with appropriate equipment, Price of this would also set you back a fair bit.
Steel capping/channel is fairly cheap, and fairly nasty too, however this would do the job and give you the protection you require, obviously is not as good as a deeper chase and using round or oval PVC conduit in permitted zones
Otherwise PVC conduit and cables must be run in permitted zones which is vertically below and above sockets, and directly horizontally to accessories etc