If you plan to play a game like Hogwarts Legacy and you want to play this in 1440p with Raytracing, you might want to go with the 4080. My system is using 13GB VRAM in Hogwarts Legacy at 1440p Ultra with Raytracing. So for next gen I'd rather have the 16GB Vram vs 12GB Vram. Before Hogwarts Legacy I was inclined to say 12GB for 1440p is enough....but it seems I was wrong. Not because of its compute power....that is absolutely fine. But 12 GB VRAM is borderline. Ok now....but future proof? Not sure....
Regarding your bottleneck question. Yeah, you will see an insignificant bottleneck. No need to worry about it...