upgrading hard drive to SSD - 2 options for SSD?

[Dramus75]

Hello,

I am interested in updating the current 5400 RPM SATA HDD in my HP Pavillion x360 14m-ba013dx laptop.   I would like to install a solid state drive (SSD) instead, and have Windows 10 run on that.  I don't really have a need to keep the HDD (even for data storage).    I would like some clarification after reading the Maintenance and Service Guide (document #926140-003).   

The Maintenance and Service guide has sections on Solid State Drives - "M.2 type" - and lists models that will work with the computer (page 21 and page 45).   The installation instructions for the SSD are shown on page 46.   It looks like the motherboard has a slot that accepts M.2 type SSD.  This matches they types of SSDs listed on page 21 and 45 that will fit this slot (M2. type).   Before reading the manual, I was under the impression I was  (1) removing the current HDD (2.5 inch x 7 mm)   and (2) putting a new SSD in its place (2.5 inch x 7 mm type - not M.2. type).   I didn't know anything about the slot on motherboard for the M.2. type SSD.   

My first question is  - are both these options above available for installing a SSD?  The maint & service guide does not talk anything about putting a SSD in place of where the HDD was.  Will that work?  Should I be putting a M.2. SSD in or a 2.5 in x 7 mm type SSD in?   (or will both achieve basically the same thing?)  I am confused where the SSD needs to be installed after reading the service guide.   

I had one other quick clarification question as well:   page 1 of the service guide (product specifications) - under the MEMORY section, it says "Two SODIMM memory module slots, non-customer-accessible/non-upgradable.   Supports up to 12-GB of system memory".  Why does it say "non upgradable" and "Non accessible"?    This laptop came with 4 GB, and I'd like to upgrade it.   page 62 of the guide goes on to show how to do it - so why is it "non accessible" and "non upgradable"?   I would like this clarified - can I update the memory or not?   

thanks for any assistance