How to remove components in the modeller?

I am working on a custom modeller project where I want to remove all those different components that are there in the modeller and go with this simplistic and nice-looking UI for it. I want to be able to remove the existing components in the modeller and make custom components to replace them. I also want to be able to modify the properties panel on the right to reflect this new design and change the different properties. Would love to hear from you on how to do this. Have been struggling to understand how to achieve this goal.
Thanks for your time.

We all want nice-looking things. Please be more specific. You want to change the way the palette, the context menu and the properties panel look? Is it only about the styling or about the functionality, too?

So the styling will be changed but also we want to be able to add some functionality to the properties panel. We want to add some other fields that can be filled in and also have pop-up menus open to select from templates etc. I hope this answers your question.

So a lot of different requirements then. Feel free to check out the example how to extend the properties panel: bpmn-js-examples/properties-panel-extension at master · bpmn-io/bpmn-js-examples · GitHub

Thanks, will go thorough it.