1.
Galax is only a new branding of KF2 and Galaxy. It is not a complete new company.
I bought Galax GTX 970 EX OC in October 2014 and I am happy with it.
2.
GTX970 is the more bang for buck to GTX980. Yes, only 10% slower than GTX980 as long as you do not need real 4GB VRAM. GTX970 has only 3,5GB VRAM on high speed.
If you play games only on 1080p, just save your money and get GTX970 instead of GTX980.
3.
GTX970 from MSI's and Gigabyte's (G1) are also very good. Just be careful with G1, this card is a bit bigger than Galax GTX970 EX OC and MSI GTX970 4G. You might want to check if your case can still fit the Gigabyte G1 GTX970.