I rode through those areas in June/July. I Siberia towards east the moskitos started to be a plague, clouds of them follow you, I have a short clip of that phenomeanon. Although there is nothing much in mid Kaz. I loved it. I rested my eyes and my mind while riding through this land of nowhere. It´s amazing how much space I´ve experienced there. It was wonderful for me. Others find it boring, or not interesting...I love it.
There is much to see in the Altai region without touching special permit areas. And it´s easy to find backroads, in my case: they always found me, there was nothing more to wish for.
For Siberia: take
local moskito repellent, this will cost you some days of your lifetime, but it works.

And take a moskito hat, to avoid strolling around with your helmet on. ;-)
For Kazakhstan: carry a camelback. It´s really hot in summer! If you like deserts, go there. Camping is easy, riding is smooth. Don´t speed if you see any shadow ahead (i.e. under a bridge), that´s where the cops are hiding from the heat and they will hassle you if you were speeding or crossing the line.
For Kirgistan:
always carry some 10$ bills on different places on you. you might need them for bribing.
For eastern Russia:
no more camping for us, first of all, we were warned abot criminals, and wildlife.
And I really liked the long roads, just like Kaz. but with trees.
To your 1. post: I would definetely rush through the states :-)