There have been both changes to the P2P protocol that prevent this, and changes to the way that nodes are discovered.
The method which 0.1.0 discovered new nodes was by joining the #bitcoin channel on freenode. Your IP address would be encoded in a certain way and that would be the IRC nick for your node. However this has long since been removed ...
I've read that addresses alone are a "confusing" way to think about "where" bitcoins "are".
Yep, addresses are only an encoded description of how the coins are locked, not when(*) they are.
e.g. back in 2018 getaccountaddress would list 1 address, getaddressesbyaccount would list that plus a 2nd address, getaddressesbylabel ...
For future reference, thought I'd respond to my original question with what I've found out to this point. Haven't fully answered the original question yet but the approach I'm using at the moment to toggle between wallets is:
bitcoin-cli -rpcwallet="filename" [command]
Any other thoughts on best practices would be great!