Windows and Office are incredibly easy to generate an activation key for using MASgrave. As I understand it, it tricks MS into giving you a valid Windows key, but the Office side does some trickery to fake activation.
Either way, very easy and no need to install shady cracked versions. Just install like normal then use MASgrave after.
If you want to go more legit for any reason, you can find OEM key resellers for Windows (and for Office too I think). OEM Windows keys are only good for one install, but they're also only around $30.
There's also a ton of benefits to installing Windows yourself instead of using the manufacturer's version with even more added bloatware from the manufacturer. There's a lot you can do to roll back Microsoft's bullshit through customizing the installer ISO yourself. Unfortunately it's pretty technical though. Not something easily explained in a single comment.
As a note to myself: When I get around to upgrading to Windows 11, record all the shit I do so there's at least something vaguely reputable for the community instead of bits of good info across tons of otherwise crap SEO spam articles. Remember to cite the sources too.