That's right. My more extensive changes are in Live Long & Prosper 2.0 Mod.

Did you changed the GameplayDefault.oc only?

When playing this mod - I find the AI does tend to grow very quickly in 'Impossible!" mode.

How does the AI react to this mod, does it tend to max to new limit cap or behaves like vanilla?

This specific mod has a hard limit of around 52. But you could easily change this to 999 if you wanted. You could do this by navigating to: The Guild 3\Modding\mods\EvenMoreBusiness\content\media\base\guild3\GameplayDefault.oc and using CTRL + F to find
'15 = GNobilityData // Archduke.'

Then replace:
ModifierEffect
{
Filter = "IsFamilyMember";
ActorValue = "MaxOwnedBusinesses";
Mod = 6; //Total: 52
Recover = true;
With
ModifierEffect
{
Filter = "IsFamilyMember";
ActorValue = "MaxOwnedBusinesses";
Mod = 953; //Total: 999
Recover = true;

Is there a hardlimit about how many business someone might own?
In the endgame I would prefer be without a limit at all.

Once the games been launched from the mod launcher. The game should begin it's usual start up routine as if it was launched directly from your steam library.

can i start the game via the normel way once i opened it via the mod launcher once?