Dimension 9200 clean install

I have a Dell 9200 PC that is running very slowly on W10

After all usual stuff, clearing junk, malware check, defrag etc., still not good enough - as its currently on an old HDD, going to install an SSD for the OS.

Been advised to do a clean install rather than clone across an OS that might have issues.

This SSD will come from another W10 PC  (one I'm using today)   I will install a new larger SSD in this main PC (using Clone SSD software) so that will be easy enough.

I have 2 questions ....

 Do I need to wipe or change something on this SSD before I install in the Dell  - is there a boot log or something I need to delete to avoid it trying to boot off this 'wrong OS', or will using install media override that.

The Dell 9200 is currently all working on-line, and therefore full valid W10 licenses ... but I have no license code (was upgrade W200 > W7 >W10)

I had to delay upgrade for months as I could not find admin account password .......... I have now found this, so want to 'protect' myself, against being locked out again after upgrade.

How can I get to view the account & license details, I have full access form admin account.

Just don't want to get the 2 OS versions mixed up and end up being  locked out of PC.