So what might have been Elan's super secret plan?

[Peelee]

He wasn't referred to as Blondie in either of those two films.
What is your source, or your basis, that it takes place before the two Dollars films?

From Wikipedia:

The Good, the Bad and the Ugly is considered a prequel, since it depicts Eastwood's character gradually acquiring the clothing he wears throughout the first two films and because it takes place during the American Civil War (1861–1865), whereas the other two films feature comparatively more modern firearms and other props. For example, Lee Van Cleef's character in For a Few Dollars More appears to be a Confederate veteran who has come down in the world, and a graveyard scene in A Fistful of Dollars features a gravestone dated 1874.

Unless the Civil War takes place at different dates in the Dollars trilogy, that one has to be a prequel.

Can I just say this is the weirdest hill for any of you to die on

You should see me talk about the World Between Worlds in Star Wars.