I've never heard of having more modules affecting an app's performance, and yes, it makes sense to separate modules by business logic for maintainability and reusability reasons.
Have more modules doesn't affect your performance. Having a lot of features, data and bad modeled logic and pages will.
Where the first 2 might be related to the amount of modules.
Now my laptop is very slow with more than 20 modules, What is system requirement for deloper ‘s laptop for dev mendix?
my : core i5 with ram 16G