Thing is I updated to Mojave last week across all my machines. And now all my machines run way hotter.
As for battery. I use istat menu pro monitoring rather habitually and my inactive wattage usage has remained the same or gone down half a watt from stock.
At use, hard to say as metal uses a lot more watts on both my Mac and iMac.
Heck my iMac saw almost a 50% average wattage increase from 10.3 to 10.4.
It should be noted that there typically is a significant difference in performance when comparing the Apple 256GB SSD vs the Apple 512GB SSD (due to interleaving the data transfer in larger size SSD's).
From a couple of random reviews using the Blackmagic benchmark of the 2015 13" MBP:
256GB write: 575MB/sec read: 1333MB/sec
512GB write: 1417MB/sec read: 1336MB/sec
It should be noted that there typically is a significant difference in performance when comparing the Apple 256GB SSD vs the Apple 512GB SSD (due to interleaving the data transfer in larger size SSD's).
From a couple of random reviews using the Blackmagic benchmark of the 2015 13" MBP:
256GB write: 575MB/sec read: 1333MB/sec
512GB write: 1417MB/sec read: 1336MB/sec