How do you decide which UI components and layouts work best for different ERP modules?

Hello everyone, I'm building a custom SaaS ERP, and I'm trying to understand how experienced developers and UX designers decide which UI components and layouts are actually right for each part of an application. For example, accounting, inventory, sales, purchasing, and HR all have different workflows. How do you decide when to use tables, cards, forms, tabs, dialogs, sidebars, or completely different layouts? Is there an established set of UX guidelines or standards for making these decisions, or does it mostly come down to experience and testing with real users? I'm also curious whether you follow a particular design system or use existing ERP software as a reference. I'd really appreciate hearing how you approach this in real projects, especially if you've worked on complex business applications.