Is there a way I can group screens and tags based on customer to keep everything tidy for large scale?
Sure, all your objects (screens, I/O tags, calculated tags, historical values) can be both named (so that their naming convention contains identification of customer/purpose) and assigned to logical groups.which serve exactly this purpose - to organize large-scale projects
https://doc.ipesoft.com/display/D2DOCV12EN/Logical+Groups