- Yep, you can mount 2 140x27mm fans on the bottom, no problem at all. You only have to make sure that your motherboard is standard ATX and doesnt have any big connector in the bottom end that can be blocked, like 90º USB 3.0.
- The front fan can be as wide as you want, as long as your GPU allow...
I can only speak for myself, but I use 120mm fans in the bottom because I had two NF-A12x25 Noctuas and they are better than any other fan, 140mm models included.
In terms of CPU cooling, NH-C14S is still your best bet. BeQuiet offering is almost as good, but I think the reason behind his low...
1- Front intake and bottom/top exhaust. I think is the best option in terms of airflow.
2- With two radiators and quality fans, like the Noctua NF-A12x25, you can have a silent PC even with a "balls to the wall" HEDT platform.
I had a H100i PRO before and changed it for the NH-C14S (one 92mm rear and two 120mm slims in top, all exhaust), and the results are great. Cooler and quieter GPU, cooler RAM and M.2, and very similar CPU temps.