Any tower cooler that fits that socket will work. The cryorig h7 it pretty good, same for the freezer 33, even the classic hyper 212 will work just fine.
You can just get any of those that it on sale or the cheapest right now.
I'll recommend a separate modem and router. Because you can always change out the router for a better one, with lots of options to choose from. As for a modem/router combo, I think there aren't that many great options out there now.
Ok. Sorry I didn't know that. I've seen systems with both quadro and geforce working, as long as they are in the same generation, which the p600 and 1070 should be.
It should not matter, the driver will just find the suitable cards for each other. Besides the P600 and the 1070 are not even the same GPU core underneath, so there should not be any conflict.