You’re probably looking at an older GitHub page for ICRC-7, latest NNS voted version can be found here ICRC/ICRCs/ICRC-7/ICRC-7.md at main · dfinity/ICRC · GitHub
Most WG GitHub repos have various standards that are currently or previously under discussion, but only the standards in the ICRC repo above are considered finalized and passed NNS voting.
Regarding the relation between ICRC-7, 37 and 3, you’re correct.
There are currently no plans to replace ICRC-7 at this moment within the NFT WG, future plans intend to extend ICRC-7 with more functionality similarly to how ICRC-37 is an extension.
The ICRC-97 Metadata standard is currently an ongoing topic, any feedback would be highly appreciated Request for feedback: ICRC-97 NFT metadata standard
As for the implementation link in your post, yes that’s the current implementation made by one of the active WG members that I’d recommend. More implementations in e.g. Rust are being worked on.
Really appreciate the feedback, when I find some time, I’ll look into the WG GitHub repo and make PRs where necessary to clear up some of this confusion.