Notebook Hardware and Upgrade Questions

Hello,

I have a couple questions regarding a ProBook that I am considering buying. I need a new laptop for school and the ProBook 450 G5 is a top contender. However, customizing it has some limitations. I am able to get everything I want except for an M.2 PCIe NVMe SSD. Yes, I can add a 512gb option in the customization, but HP is charging $462 for this, which is ridiculous. I'd like to buy a Samsung 970 EVO 250gb on Amazon for $78 and once I receive the computer, put the SSD in. First, would this work and, second, would it be easier to clone the HDD that the computer comes with or install Windows to the SSD with a recovery drive?

My last question is that I don't think I need Windows 10 Pro so I'd like to go with Home instead and save the ~$80 that HP is charging. (I like the BitLocker feature with Pro but don't think that's enough for me to spend the extra $80 given that I wouldn't use the other extra features of Pro.) However, the customization is saying that I can't have 8gb of RAM and the FHD display with Windows Home. This doesn't make sense to me because it is Windows 10 Home 64-bit which supports well over 8gb of RAM. Basically, with the FHD display option, HP will only allow me to customize with 4gb of RAM, which will not suffice. Thus, I'd like to buy this 8gb stick of Crucial on Amazon (https://www.amazon.com/Crucial-Single-PC4-19200-SODIMM-260-Pin/dp/B01BIWKP58?th=1). Does this seem plausible or am I missing something?

Thanks in advance for everyone help.