No. A Kill-A-Watt can't measure anything nearly as fast as an excursion spike from a graphics card. Not even Nvidia's own PCAT can do that. You'd need an oscilloscope.I have a Kill-A-Watt meter but I don't think it can react fast enough to catch very short power spikes.
It depends on what you're doing with the PC. Many games and benchmarks, you won't see a problem. I "intentionally" see if I can make a PSU shut down with Ampere cards by running Prime95, all cores, small FFT’s and Furmark 1080P w/ 2X MSAA & Post FX. Hit the space bar a couple times. Only need to run for about 3 to 5 minutes. If it doesn't shut down, you're solid.From what I can make out people compensate for the quality of the psu by increasing the wattage rating...I have seen a YouTube build of a SFF system using a FE 3080, 9900k and Corsair SF600. Now that did make me cringe give the CPU’s power needs but the system past all the benchmarks and games they threw at it with average scores.
If you're just going to use a 3080 to get 30 FPS in COD Black Ops Cold War, you're probably fine.