Everything I wrote is based on my experience playing Heroes.
Which of the Heroes rules options are most often selected?
The standard options for banning objects and for allowing town rebuilding. If it's version 1.40, then the option for allowing library rebuilding.
In the released version of the window, is it possible to reduce the size of the object ban selection?
Of course, because the object bans for the map editor, Hillfort, and Keyholder are set by default, almost automatically. I think in 98% of games, everyone sets them.
Is it possible to group and reduce the size of some other Heroes options in a similar way?
Nothing better comes to mind than creating a similar window for rarely used settings, such as: [2d lvl structure], [2d lvl stack], [1-way monolith], [1 DD per day], [pvp battle with neutrals]. Because these settings are rarely used.
Do people still play without allowing town rebuilding?
I don't know of anyone who does. Almost all games allow town rebuilding.
Where should the 1-way monolith option definitely not be enabled, or where should it definitely be enabled?
This option is usually not used, except in rare cases.
Once again, which options should be linked to map sizes or templates, and which should be removed from this list?
I think the timer should be linked to templates. Perhaps the standard market bans should be linked to M200 templates.