How big are the drives? If they're under 1tb you could image them onto (4) bigger (eg 24tb) drives and then scan through those images a lot easier. It's might be worth considering they're lost though if you keep writing to them and haven't put them in areas they'd be protected (or backed them up).
It'd make sense to search for strings like "electrum" and "default-wallet" it'd also make sense to try to work out how electrum stores encrypted and unencrypted wallet files and find a string from those (but I'm not too sure how they're stored).
That's exactly what I have done. I have two 20TB external drives which I've imaged everything onto in their own image files (Disk Drill is fantastic for that).
The issue I'm running into is I see pieces and references to electrum but I'm wondering if there are any beginning-of-file bits or common hex strings that I can search for which would show me the beginning of a wallet file.
The paths are gone because I am sure when I gave up with BTC I just deleted the install. But i know the data is still there. The drives have been untouched for all these years. Just sitting in a box. I've also used unerasing tools to no avail. That's why i'm down to using the lowest level type of search - hex editor/search tools.
Thanks