I understand that I can specify the wallet via the
-rpcwallet="walletname"
option. But for what purpose are the loadwallet/unloadwallet commands? How are they meant to be used?
I second the post above but I think there's no issue on your side, the command is to load the specified wallet.
You got that error of
Duplicate -wallet filename specified because that wallet was already loaded as you created it.
You should use that the second time you use Bitcoin core after your exit your current session.