About the bonus question, its all about bus width
Steam deck has a 128 bit memory bus, whereas the Xbox one has a 256 bit memory bus.
Channels are also mostly desktop terminology, they are technically part of the DDR spec but they change around so it's easier to just compare bus width. Steam Deck has 4 32 bit channels, while Xbox One has 4 64 bit channels.
You are also confusing the clock speed with the transfer rate, the memory in Xbox One switches at 1.066GHz and transfers at 2.1GT/s, since its "DDR" or "dual data rate", which means that it does a transfer with both the rising and the falling edge of the clock.
End result:
- 256bit * 2.1GT/s / 8 = 67GB/s
- 128bit * 5.5GT/s / 8 = 88GB/s
(the division by 8 is there to go from bits to bytes)
Is there any “non proper” RAM manufacturer anyways?
All ram packages come from like 4 companies, and memory nearly never fails anyways.