It's a MacBook Air... Apple isn't targeting the gaming market with this machine at all. I'd invest in a MacBook Pro or if gaming is really your primary need for your portable, get an Alienware. Game selection is much better on Windows.
My understanding is that it's some sort of modified SATA to be smaller. As for the RAM, honestly, I wouldn't even try soldering it in. First of all, for all we know, the motherboard can only handle 4 GB, which is unlikely, but possible. The costs of 8GB of ram and soldering service.... I wouldn't want anyone to screw up my motherboard My guess is that if it was feasible, Apple would have allowed it but for a hefty price. I guess we'll have to wait for next generation. The SSD should help mitigate some of the RAM bottlenecks because it's a faster scratch disk, unless you're doing a lot of VMs, in which case you shouldn't have gotten a MacBook Air. OtherWorldComputing has some very fast SSD upgrades for the MacbookAir you can install yourself easily. Hope this helps :)