The GSKILL Memory and Corsair SF power supply look like good options. Corsair also has a 750W option if you plan to buy ahead of the launch of the new graphics cards, which could have power consumption 100W higher than current flagships, although even then the 600W should be fine.
Rumor has it that Samsung has an M.2 NVMe PCIe 4.0 SSD coming out in the next few months (Samsung 980 PRO which could have speeds up to 6500MB/s)
Also, if you're considering a dual radiator setup in the NCASE M1, then ASUS's X570 ITX board may be a better choice than the DTX. A dual radiator loop is a tight fit and the larger DTX motherboard as well as it's riser card for the M.2 SSDs could make fitting the second radiator difficult.
Looks like it's going to be a really nice build!
Also, I just noticed that Amazon has resumed shipping to South Africa, albeit with limited and rather expensive shipping options, but there's a chance that we'll see more product range and shipping options being added over time.