No. Not overkill.
Cpu sets the frame rate. It takes the game code and pre-renders it, puts dimensions, placements, movements, user interactions etc. It'll do that to the best of its ability. The amount of frames it can complete in 1 second is the fps. Then sends that to the gpu, which takes that frame, adds color and shadow etc and paints it on screen according to detail levels, post processing affects and resolution. It'll do that to the best of its ability. The amount of frames it can complete in 1 second is the fps you see on the counter.
So if your old cpu can do 100 fps in a game, it sends that to that decrepit GT730. Which at low details can only stick 50 on screen. Bumping up to the 1650 will allow all 100 from the cpu at high-ultra.
If your cpu is only capable of 50frames and that GT730 could put all 50 at ultra (that'd be a very old DX9.0c from like 10 years ago) then a move to the 1650 won't change anything, same 50fps output since the cpu is capped.
The only thing a gpu changes is detail levels at any given resolution. It either can live upto what the cpu gives it, or fails.
Right now, that old GT730 is almost always gpu limited in fps output, playing anything relatively newer is low settings just to make it playable. The 1650 will be the opposite, you'll be at high-ultra easily and cpu capped, but that's only temporary until you move to a stronger cpu/platform.
The Vega8 graphics are superior to a GT730, right at GT1030 levels, but the tradeoff is you'd be going back to a weaker cpu when you do move to something like the 1650 and the Vega graphics would no longer be used, wasting half the chip on nothing.
By itself, the 3200G/3400G and Vega graphics are seriously impressive, but if you plan on upgrading to a full discrete gpu, the Vega is moot and you'd be better served with a seperate cpu/gpu combo.
So it's a choice, go with just the APU and call it a day, or upgrade gpu now and get a good matching cpu later.
A r3 3300x is $119, a 3400G is $149. You are paying more just for the Vega and the 3300x is a stronger cpu than the 3400G on that side of things.
I could live with overkill temporarily, not so concerned with immediate gains, more concerned with gains when I'm finished.