Yes, it is possible to change the general settings UI without modifying the code directly. You can achieve this by installing a free backend theme from the Odoo App Store. These themes allow you to customize the look and feel of the Odoo backend without requiring direct modifications to the source code. You can explore free backend themes here:

🔗 Odoo Backend Themes

As for displaying only your custom module in the Apps module, this can be done without additional customization if the module's author has set a default domain to filter by author. This ensures that only specific apps are shown without needing further configuration.