Well, the normal way to update a PC or laptop from HD to SSD OS drive is simply to clone the drive, turn the machine off, switch the drives and re-boot. I have done this mroe than once with Win 7, so I'm not sure why it would not be possible with Win 10?
As I understand it, Windows locks itself to your motherboard, so if you change that, it then thinks it is in a new system and wants you to re-authenticate (or possibly buy a new copy of Windows)
... but changing a HD for an SSD shouldn't be an issue...
My approach is likely gonna be to clone my Win 7 systems to spare HDs before I make the upgrade, just in case I get any nasty surprises once it is done....