The issue is that you are going to a newer generation processor and newer generation chipset. What happens is that all devices will need to be re-enumerated because of the perceived hardware change(s). The way Windows works, some of this re-enumeration doesn't occur until after you log in. If it happens that the keyboard is not enumerated until after login, you have a Catch-22 situation; you have no keyboard with which to provide the password. I have been successful recovering from this situation once or twice, but most times it took a reinstall of the O/S from scratch to get it back.
Bottom line, this might or might not work. If you try, the way I successfully recovered was by rebooting in safe mode, letting it sit there for a while and then rebooting normally. Sometimes, after a few cycles through this, things will suddenly start working (moving to and from safe mode sometimes seems to change the enumeration order). Again, I have been successful with this once or twice, but the bulk of attempts failed miserably. My recommendation is to bite the bullet, install Windows from scratch and then transfer over your data files and apps. This is a pain, I know.
Something else: The WY system utilizes an mSATA SSD whereas the RY system utilizes an M.2 SSD. You are going to be doing a transfer of data no matter what...
Are you familair with sysprep? The following steps will make the final part of Windows installation run again and you will need to make a new users and have drivers. Good thing is download all drivers and keep them on SSD in root folder for easy access later.
Start a Admin Command prompt and goto %windir%/system32/sysprep (You can start admin CMD by pressing Windows key and X, then A)
See if you have sysprep there, if yes, run sysprep /generalize /shutdown
This will unload all drivers and shut down system. Attach hard rive to new system and you have to reactivate with key again and make a new user but your old user content is still there in same directory under /users.
Scott is 100% correct. I have experimented with this myself with limited success, moving from a D52450 to a NUC5i7. I've tried with Windows 7 (worked, but had to reactivate Windows), Windows 8.1 (had the enumeration issue Scott mentions, so was a complete failure), and Windows 10 (worked, but treated it as a fresh install and set everything up like a new user).
I hope this helps.
In regards of the RAM it seems that is compatible with the NUC that you will get. Now, with the storage you will need to get a M.2 drive and if you want to add another one you can use a 2.5" SSD on that same NUC. You can see the list of compatible parts for that NUC on the links below:
It is very important to use supported hardware to avoid any potential issue with the device after you have it ready to be used. You can also get its full specifications on the following link: ARK | Intel® NUC Kit NUC5i5RYH
If you have more questions please let me know.