Just double check on your board’s support page about the bios. On my asrock ab350 pro 4, the bios I had to use was a beta bios that added support. On the AsRock support page the bios version I needed wasn’t listed at the top with the normal bios versions but at the bottom.
I do concur though, I considered the same thing, unless you get some kind of a deal, don’t bother with the 5700g. Not a bad cpu but if you’ve already got a gpu and are planning to game, skip the 5700g and go for the 5700x as there is a bit of performance hit.
Personally I went ahead and got the 5900x because of higher core count and more cache. However I’m not sure without looking about info on your board. Plus you’d need a better cooler. So the 5700x does make sense in that respect because it’s a 65 watt cpu.
Also, did you ever check the label on your power supply? If you let us know what it is we can provide feedback on it as you don’t want the power supply to go out and damage parts. I know you said it’s a 750 watt, but quality of units can vary. As you are upgrading and tuning you don’t want your power supply to die and take out any of your other components.
If the power supply is a decent one I think you’ll enjoy the new cpu and ram. I had a ryzen 3600 before going to the 5000 series and that was a decent pick uplift. So from a 2600 to 5700x should be a good jump to tide you over until the next pc build.