Hi y'all.
I installed the HotA and saw that I can't play vanilla campaigns.
And asked around a bit and I was instructed to click the HD launcher and in the top left swap the h3hota exe for Heroes 3HD, that would launch the HD+ mode where I can play vanilla game with HD graphics instead of HotA that is focused on multiplayer.

I was unable to do that cuz there are only h3hota and h3hotaHD launcher options.
Keep in mind this is possible with the HotA mod downloaded directly from the modders website.

After a while I found that this is cuz the mod should be installed in the main HoMM3 folder not in it's own separate folder as it is installed by default using gog version.
But when I myself change the install path and install it directly over the main folder it works, but with glitches, (main screen in game has a glitch and campaign missions intro movies are black, only subtitles).
And uninstall didn't work as it should cuz it was overwritten by the uninstall from the mod.

My only solution was to download HD+ and install it in HoMM3 folder, and use that when I want to play vanilla campaign.
And use gog HotA when I want to play multiplayer.

Not sure if this was intended like this. Just thought to report it.

Ah, I see we've run aground of one of the first obvious questions that even some youth would have asked, "Will this work with other mods", which seems to be iffy at best.

The HD+ Mode is available as a separate download and as part of HotA.
If you download HotA, you should not have to download HD+ on it's own.

After you install HotA, if you find and open HD_launcher.exe, in top left drop down menu you should be able to choose between hota and heroesHD exe.

It's useful because by default you can't play vanilla campaign in HotA, you can do it with HD+ mod.

And for new players I imagine it would be useful to go through the campaign first, and learn the game slowly, and for lore.

Again, this is possible with HotA download from the dev website, and not from gog.