Your setup should be more than fine. And yes, you're right, there are some PCI lane limitations with the B450 chipset. I only have 4 SATA ports which is fine for now but could be an issue in the future. However it's nothing a HBA card cannot fix.
I don't have a Kill-a-watt or anything similar but I will try to figure it out and report back. I'm using a 450W Bronze PSU, FYI.