What can be painlessly removed from a freshly installed Win10?

Question

Windows

Having a licensed W7 HP on one of my home laptops, I decided to succumb to the general hype and upgrade it to W10. Everything went without problems, but I was surprised by the rather large amount of filling in the system partition - more than 40 GB. The question arose as to how this volume could be reduced. There are at least three reasons for this: less space is needed to store a backup of the system partition, the process of creating and deploying it will be faster, and (personal reason) I need to fit the system partition on the small size SSD that this laptop has.
The first candidate for deletion is the Windows.old folder lying in plain sight (more than 5 GB), no advice is needed here. But since this is not enough, please tell me what else? Somewhere in the bowels, perhaps, there is an installation package (ie distribution kit) that is no longer needed - but where is it? I'm also ready to give up everything related to Modern UI and Metro spot apps, since I'm not going to use them - but again, where are they? In plain sight (i.e. at the root) there are also $Windows BT and $Windows WS folders (also 4...5 GB each, there were none in W7 and W8.1) - what is it and is it possible to send them too to the side?

Answer 1

Removed Windows.old, $Windows BT and $Windows WS - the system booted up and works fine. Deleted it by booting from the tool-recovery LiveUSB to avoid fiddling with permissions and ownership. But even in this case, the NewOS subfolder containing the bootmgr file could not be removed from the $Windows BT folder.
Now the contents of the C: drive are less than 13 GB, which suits me perfectly.

Answer 2

What can be painlessly removed from a freshly installed Win10?
Everything.
Windows was, Windows and will remain ...