How ya doing?

I finally decided to get a new gaming rig, after sticking with my current setup for 7-8 years. I'm not as hardcore with the hardware stuff nowadays (I got lazy) and I'd just like some of your opinions on the parts I picked.

Processor: Intel Core i5-6600K 3,5 GHz
GPU: MSI GeForce GTX 960 GAMING 4G 4096 Mt
RAM: Kingston HyperX FURY DDR4 2666 MHz CL15, 16 Gt (2 x 8 Gt)
HD: Kingston SSDNow V300 240 GB SSD 2.5"
Power: Corsair CS550M, 80 PLUS Gold, 550W
Monitor: BenQ XL2411Z
Case: BitFenix Neos - ATX-case

So, some questions:

- Didn't even know about mSATA SSD hard drives before now. Is there a difference? They function as normal hard drives, yes? How's it compared to normal SATA connections?
- I think I know the answer already, but is 550W enough power for my setup?
- Does the case make any difference. It was the cheapest I could find. It only comes with one 120mm fan. What about possibly overclocking in the future, how many fans I would need? I don't wanna mess with water cooling.
- This is the first time I'm not gonna buy a separate sound card. Are the integrated ones any good?
- The monitor, I wouldn't have any doubts, but I've read some of the massive 144hz megathread by clerictgm and it made me hesitate. I don't really care for anything else than getting the fastest response time. Will this suffice?
- I also ordered my first mechanical keyboard, it was some off-brand. It said that it has POM-switches and PBT-keycaps (?). Tried to google, but all it came up with was that there are POM- and PBT-keycaps, no switches. Am I missing something?
- Still rocking my ZOWIE EC1 EVO. I've seen the button delay chart, and I'm wondering if I'm better off with a Logitech mouse? Or what about the updated version EC1-A? Is it worth to upgrade and spend 60-70e?

Hope you don't mind this flood of questions. Too busy with IRL stuff to really dig deep into this topic, but still a latency minimalist ;) thanks in advance