Hello
Exposure_. The 750 wattage appears perfect to me, although personally would never power my systems with a Rosewill power supply. I would only consider what I believe are higher quality units, in my opinion: EVGA, Seasonic, Corsair, and only their top tier and fully modular models. In addition to the quality, you'd also get 10 to 12 year warranties with any of those product stacks at the 750 watt level.
With that said, I have no idea if a new quality power supply would solve your problem, because you haven't stated it.
Also, completely unrelated to your question, I noticed that you have a single 16 DIMM in your system. Because you don't have a complete pair of RAM sticks in your system, you're by definition not in dual channel mode, and hence leaving a lot of performance on the table. I recommend that you purchase a 2nd 16 GB stick of the exact same brand, speed, size and chip-type,and place it in the appropriate slot, according to your motherboard manual. Looking at the manual, for a Ryzen Summit Ridge CPU, a single DIMM (SR or DR) should be installed in slot A2, while dual DIMMs should be installed in A2, and B2. If you ignore the memory slot recommendations, enable XMP, and overclock RAM to rated speed, you will very likely experience serious system and windows stability problems.
FYI: Your OLOy branded RAM is not on the Asrock Ftal1ty B450 Gaming K4 QVL (qualitified vendors list), although it's possible that this brand did not exist when they tested memory for this board. I only started hearing about it two months ago.
-- PSUs that I'd personally consider --
EVGA: G2 / P2 / T2
EVGA G3: It's probably just as high quality as above, but I've read customer reviews mentioning annoying acoustics of fan curve, therefore I personally avoid it for that reason alone.
Seasonic: Focus / Prime Ultra
Corsair: AX(i) / HX(i) / RM*
-- user PSU specs --
Current PSU: Rosewill Hive-750S
User considered future PSU: Rosewill Photo 1200 watt
-- TDP of GPU and CPU --
Vega 64 TDP: 295 watts
Ryzen 7 1700X TDP: 95 watts
GPU + CPU = 390 watts