There is no such thing as "bottlenecking"
If, by that, you mean that upgrading a cpu or graphics card can
somehow lower your performance or FPS.
A better term might be limiting factor.
That is where adding more cpu or gpu becomes increasingly
less effective.
I would think that a GTX1660S would be appropriate.
Some added thoughts on the psu:
You will find that the increased cost of 550w or 650w is not great.
Buy a psu for the long term. Look for a quality unit with a 7 to 10 year warranty.
On the cpu, since you will in time install a strong GPU, consider the i3-10100. It includes integrated graphics for starters.
It should cost less and perform better than the 3400G
Here is a review...