New GPU causing bad performance.

[coldwash]

As far as drivers, ddu would work without windows reinstall, amd has their own radeon removal tool too.

 

You could plug your pc into something like a "kill a watt" to see your real power draw at the wall, but the reality is at nearly 100% utilization psu don't neccesarily put out clean power.  1070ti is going to draw at least 90w more than what you had before in best case scenario.  If you don't believe that you need more than 450 bronze, I would say check out the videos of Linus OC'ing his 2080ti and needing dedicated ridiculous power for cpu and gpu separately, not to mention jayz 2 cents and gamers nexus.  Those guys are showing extreme cases, but you can easily see how gpu really need some clean power to run stable and that they can eat much more than they are even rated.  The reason you run more than you need is psus don't give clean power if you max them, and nothing will run stable.  Plus you will fry your motherboard and other things which are attached when the psu goes belly up.