Unless you verify that you are exceeding 16 gb of RAM, which you would kinda know as the pc would basically dog, then go with just the two 8gb patriot ddr4-3200 for 16gb total.
Keeping the existing two 4-gb ddr4-2133 will cause the new patriot ...
Always prefer 2 sticks of ram over 1 stick, it will be faster. Also (more important) get sticks from the same size to ensure compatibility.
based on those two rules, only the 2 8GB sticks will be best, and 16GB will be more than enough for most tasks (I had a VM, 8 chrome tabs, discord, teams and 7zip open this morning and only used half)
That is correct in theory, but I have not tested it myself. But Linus Tech Tips does have a video about mixing memory and his conclusion was that in dual channel mode (2 sticks) it does not matter most of the times.
That motherboard does not support ryzen 5000 out of the box, and also does not support BIOS flashback, so if you want to get ryzen 5000 working, you need an extra cpu, ram and gpu to flash the bios.
The AsRock B550 PG Riptide does support ryzen 5000 out of the box
My RAM is also not on the motherboard compatibility list (B450 + Ryzen 3 3100) and it works (really well, I overclocked it). So you can take a small risk and buy the faster RAM, or take no risk and buy the slower ram. Its your choice if the risk is worth it. (the hyperx is like <2% slower so I won't take the risk)