405 idle sounds about right. It used to be lower for a single card, but there are reasons why 2 cards can't idle the same as a single card. You can lower it using 'tools', but I'd not tbh.
Memory usage seems ok.
Peaking now and again is normal iirc. Generally if u do something and a wonderful windows routine thinks it should be accelerated (when it doesn't really).
With stock cooling, idle temps for air should be around 70 something, load around late 80s. (taking into account personal rig build qualities. I never use a case so got a bit lower, but that's not normal)
With 2 cards, the upper card should show a bit more than the lower.
Oc'd to 850 or so, the temps 'should' still be in the 90s, with stock cooling.
Dual cards will show higher temps than reported single ones, anything from 5-10 degrees, again depending on the rig arrangement.