What settings be related to new look and feel of SharePoint Online?

Hello ,

Sometimes it is too confusing that what settings are applied to the new experience of SPO.

New Experience for SharePoint Admin center.

New Experience for Document Libraries.

New Experience for Custom Lists.

New Experience for viewlsts.aspx page.

most confusing thing is that when we click to the classic mode it lost everything at site collection level and hard to get the new look and feel back.

Is Enable-SPOResponsiveUI PowerShell have any impact onto this?

Any Special option to get fully developed modren look and feel?