New machine; OS licensing; Office licensing : all just too scary

I really need to purchase a new machine (Machine 2 below). The easiest strategy will be to pass my current machine (Machine 1 below) to a family member as it stands and face all the costs associated with a new machine (OS licence, Office licence) - and in the context of new hardware these are hardly a matter for consideration. But the decision raises interesting questions over which I am utterly confused.
1 : Machine 1 is a Dell XPS purchased from Dell UK with Ubuntu pre-installed. (At the time this was the only way to get a decent spec, hi-capacity SSD drive and a non-touch screen.) I /dev/zero'd the drive and installed W10 using MediaCreationTool. Easy. Of course I got nagged for Activation and achieved this by visiting the MS site, inventing an ID and purchasing a licence against a credit card (for several hundreds of pounds Sterling). As soon as the transaction was completed Activation occurred. I never received anything in the way of a Product Key.
2 : I wish I could recall the exact nature of the transaction (i.e. step-by-step what was requested and how I responded). Could it have been through Microsoft Store? I just cannot recall.
3 : Recently this forum published a self-help procedure to identify one's own licence characteristics. (It seems to be a minefield.) I found that my licence was Retail (good!) but am dismayed that the Product Key is VK7JG-NPHTM-C97JM-9MPGT-3V66T which I gather is not unique or personal (though I have no idea what it actually is).
4 : I suspect from (3) above that I would not be able easily to transfer my licence form Machine 1 to a different machine but to be frank I have never seen a Fool's Guide to doing this that both simply and adequately describes the procedure for doing so. Can anybody recommend one?
5 : Every so often I wipe the machine entirely (i.e. /dev/zero the drive and install Windows 10 from scratch using the current MediaCreationTool). To my great relief Activation is always achieved after switching on WiFi. I deduce that in some way the machine is "recognised" as licensed and paid for. Clearly no confirming bytes are identified from the drive as it has been entirely wiped. What is it that is recognised? Some feature of the motherboard?
6 : Conversely, I have no matching confidence for re-installing Office 2019 on a newly refreshed drive and for this reason I have not attempted it. My Office 2019 licence is a single-machine licence. (I know. I don't know what I was thinking but there we are.) Will this too recognise the motherboard and assuming I follow the correct procedure, simply become Active after re-installation?
7 : Sorry to be droning on. If this is all too facile and obvious to any of you, then that is my hope! Now for Machine 2. Assuming I buy something with say W10 Pro pre-installed (probably another Dell) then, if I wipe it clean at some future date, will its Activation again be recognised (through the motherboard or whatever) as a machine that has already had installed a pukka licensed and activated OS? The capability to install a Ground Zero platform every so often is absolutely essential to me.
8 : If I am passing Machine 1 on as a running facility, I guess I will, leave Office 2019 on it and just grit my teeth and make a new Office purchase on Machine 2. But this time I will definitely go for a multiple-machine Office 365!
Thank you!
Edition Windows 10 Pro
Version 21H1
OS build 19043.1165

fergusd said:

What is it that is recognised? Some feature of the motherboard?

Right-click on the Start button --> Windows PowerShell. Then run the following command:

(WMIC baseboard get product,Manufacturer,version,serialnumber)

Windows recognizes what motherboard it is.

Your license for Office 2019 is for one machine at a time. As long as you have the product key for it, just remove it from the old computer and install it on the new computer. Activate it with your product key.

Sounds like you bought a legit retail license, which is good....and sadly is expensive.

You can either leave it on that old machine or move it to your new machine, but you cannot do both.

Activation works by taking a hash of the equipment in your machine and registering this unique fingerprint to Microsoft activation servers. Hence reason you can keep installing and it just activates. You can change a certain amount of hardware until the hash will be considered to be too different, then it is usually a call to Microsoft to activate.

All copies of perpetual license Office is for 1 computer only. The only way to get it for mutiple computers is to use Office 365. For example, if you wanted Office 2019 Profesional for a laptop and desktop, it would be $400 x 2 or $800. Office 365 allows a single user to install on an unlimited number of their own machines for $69 a year and comes with 1TB of OneDrive space.

Yes, you can reinstall WIndows from a vendor supplied machine and it will keep activating...as long as it's the version (Home or Pro) that was installed on the machine to begin with.