Well hello there.
That's true, first gen Ryzen had lots of RAM compatibility issues, but then the AGESA update rolled in massively improving things. And the 2nd gen chipsets (so B450 and X470) should have next to no issues running most RAM sticks.
Now, an interesting fact, G.Skill are actually selling a Ryzen-optimised version of these RAM sticks, signed F4-3200C16D-16GTZRX (yours don't seem to have the 'X' at the end). BUT both should be able to cooperate with this PC.
With the boot issues, I'd check again if the BIOS is up to date and then look into the motherboard's installation instructions to check whether you've populated the proper RAM slots for 2-stick setup. I'd also take a look if everything on the motherboard is seated properly (memory, GPU, CPU...). If that didn't work, I'd load default values in BIOS and then check if the RAM will work at, for example, 2133MHz with 16-18-18-38 timings (rest to Auto; this seems to be the default setting for these) and maybe try some fiddling with XMP profiles. Some people also reported that disabling RGB lighting on these helps with stability for some reason.
And Ryzen likes to have high-speed, low-latency ram when it comes to performance. Compared to Intel, it actually makes a difference between like 2400MHz and 3000MHz.
Also, if you're running your games in your native screen resolution, then damn right you're going to have some issues with running i.e. Far Cry 5 on Ultra (look at the benchmarks https://www.techspot.com/article/1600-far-cry-5-benchmarks/page2.html
). Your resolution is kind of between the 1440p and 4k from these benchmarks, so the results are rather expected. The solution would be to either fiddle with the graphical settings and lower the most taxing stuff (the best candidates being the least noticeable ones) or lower the resolution.
As for PUBG, https://www.reddit.com/r/PUBATTLEGROUNDS/comments/76l8d1/bad_fps_stutter_with_gtx_1070_i7_cpu/
. CS:GO will push lotsa frames on any non-toaster configuration anyway. Orisis: New Dawn seems to be hated by people for having such FPS issues all over the place and being generally terribly optimised (installing some patches might help).
FreeSync (and G-Sync too) does not increase frames per second - it improves stutter, latencies and stuff like tearing. FreeSync requires AMD graphic cards and G-Sync used by NVidia requires a special chip inside the monitor - which effectively limits your buying choice to a certain number of models and these guys usually cost about $100 more than comparable FreeSync options. You could limit your ingame FPS to something like 60 or something to see if the tearing and stutter will be gone.