600w is sufficient.
But, EVGA makes some good power supplies and some not so good.
I think the BR is in the latter not so good category.
On a quality build like this, do not go cheap on the PSU.
Seasonic as mentioned above is always good.
I would spend a bit more for a Seasonic focus 650w unit.
Newer units support some of the modern low power C states.
As to overclocking, yes, ryzen is designed to be overclocked, and you should do so to get best gaming performance.
On the graphics card, not so much.
Graphics card vendors bin their chips and use the better ones in factory overclocked versions
that they can sell for more. You may be able to OC more, but then again, perhaps not.
They try to differentiate by adding cosmetics and fancy coolers which also sell for more.
I do think you get fair value from a modest factory overclocked card.
If you need more performance, they buy a higher tier card in the first place.
ditto on ram, the 3000 speed is what the ram is certified for.
You might do better, but I do not think it would make any difference in your game/app performance.
More importantly, if you need 32gb, buy it in a 2 stick kit to avoid problems,
Normally, for a gamer a single 2 x 8gb kit is sufficient.