A patch to optimize memory usage, a new clean profile, no questionable or resource-intensive mods, remove all custom maps and campaigns that could affect the map/campaign, and avoid making 100500 saves during a playthrough. If that doesn't work, which is highly unlikely, just don't play on those.

Added 5 minutes ago
I wrote something silly here and deleted it later.

Added 1 hour 10 minutes ago
No, you have too few options by modern standards. It's not worth adapting to older versions, and it's not just for Heroes of Might and Magic.