HoMM3 HD bug reports.

Campaigns and single-player maps should be played WITHOUT the HotA ruleset (it's only for online games), and also WITHOUT the HD+ checkbox, preserving the original game mechanics.

Rather, preserving the shortcomings of the original interface and the original bugs. If you don't go overboard with plugins, there won't be any changes to the mechanics.
Go on, tell me more about how I should play.

Added 8 minutes later

In single-player, the HotA rules are enabled/disabled with a checkbox in the options...
I forgot about the campaigns; the rules are probably enabled in them now.

That's the point, they can't be disabled; the checkbox is there, but it doesn't matter; at the start, there are 5 resource points and 2500 gold, and even if you click "replay scenario" in a game started before the update, these new features will also appear, and yes, as always, they forgot about the campaigns.