The new features added to the Snipping Tool are arguably the more useful, at least right now, and could probably be back-ported to Win10, though I've no idea whether they will or not. It will let you select text in an image, and then automatically OCR it and copy the results to the clipboard. You can also select text and have the Snipping Tool redact it.
windowscentral[.]com/software-apps/windows-11/whats-new-with-snipping-tool-on-windows-11-september-2023-update
Copilot OTOH is more an added interface to the Bing Chat already present in Edge. Plugins could make it much more useful, or not -- we'll have to wait and see what's released in the future from companies like Adobe, who is, per Microsoft, already on board.
windowscentral[.]com/software-apps/windows-11/windows-11s-new-ai-copilot-is-too-slow-to-be-useful
Unfortunately, after a quickish Google there doesn't yet seem to be a way to uninstall Copilot & reclaim the disk space it uses. And since it can't be uninstalled, we don't know yet how much disk space would be freed, and if it would be worth it. Getting rid of the Taskbar icon can be done in Taskbar Settings, but to actually turn it off you need to use a policy.
neowin[.]net/guides/how-to-turn-off-or-remove-windows-copilot-on-windows-11/