Just bought the second pack at TH10 which included the level 2 inferno... but I have not placed it yet, it is showing as an 'unplaced building'. After doing a bit of research I can confirm that this DOES NOT affect war weight as the unit is nowhere on my main village or war base, therefore I am still being matched against TH9s (or TH10s without infernos). All it really means is I get the gems, and in a few weeks/months when I have all my war troops maxed at TH10, I can drop the inferno with zero build time and it'll be level 2!
My miner attacks in the war straight after the update were both fails, definitely nerfed! I've gone back to govaho and we're doing okay (won 10 from our last 15 wars). If anyone in clan ocuk is now maxing at TH9 and ready to go to TH10, do not buy (or at least place) inferno towers! It's all about the war weight.
edit: At last, 1000 war stars!