pritch

It's best to have balanced intake and exhaust of airflow through a case for equal pressure esp. when running a graphics card that dissipates heat into the case. But sometimes differences aren't as great vs. negative pressure as some make out. If running at stock clocks and correctly applied thermal paste, it may not be too bad. If you don't want to return the case right away, build it up, take your time if it's your first build and don't be hard on yourself. You will make some mistakes, I still do after 15 years. When you get it all together see how it runs under load. You may be fine at stock after all. Does the case any provision for front fans at all?

Ah ok I had another look, just doesn't have direct air intake over the fans. But that's definitely better than nothing. You would probably be fine with 1 front intake and 1 rear exhaust. But if you want 2 at the front, you might want to run another at the top to exhaust as well. These should all be at relatively low speeds.

Unless the PCIe slots are meant for the graphics card, they come from the chipset, not the CPU. Even then, if something else is in a slot meant for graphics cards, the graphics card gets 8 lanes (assuming you have one card), which for the 1070 doesn't affect performance all that much if at all.
 
However, running a RAID 0 NVMe setup is pointless for most consumers. There's not event a really appreciable difference between SATA and NVMe as far as loading times go.