If you want to transfer ownership, you need to transfer the NFT. That's it. The only reason I mentioned optionally including a physical is because some people may want to load the NFT on to the art piece.
Does each respective blockchain for different pieces accept tokens/NFTs?
I know that BTC uses XCP....and Dogecoin also has tokens.
Do these cryptos haven tokens available?
LTC (Litecoin)
PPC (Peercoin)
BCH (BCash)
Also, is there a significance to the
BTC symbol being orange or neutral on the middle back of the prints?
I have 2 of the same print, but the back is different:

All the NFTs will be on Ethereum at this point. The imagery on the art piece is independent of the NFT. Having said that, it is our goal to allow the NFTs to travel to other chains via bridges.
We used two different printers to create the CofAs. It looks like the neutral was just a misprint.