With Viper the magic seat I believe is supposed to be the first row on the last car, but in my experience it's painful no matter where I sit. I've retired from riding Viper.
For X2, outer is almost always rougher than inner, and the bigger you are, the rougher it is likely to be. X2 is worth the abuse though, especially for that first drop, which for my money is the best first coaster drop in the world.
Crowds will definitely be light in January, but if you're made of money and want to be lazy, on some days there may still be a small advantage as some rides may be on one train ops due to off-peak-season maintenance creating longer than usual waits. That kind of thing is more common in the winter.
The closest hotel to the park is Hilton Garden Inn right across the street, it's the only one that's roughly walking distance. I think they still offer a shuttle, but I find it much more convenient to drive so you can easily leave the park and come back in the middle of the day. There are a handful of other nice hotels a few minutes farther away, there are quite a few within about 5 minutes drive of the park.
I see you're coming from Maryland - I will be out in your neck of the woods for the first time end of sept/beginning of oct. If you have any of this kind of info for me for SFGadv or Hersheypark, PM me! Planning on doing SFGA on Sunday 10/1 and Hershey on Saturday 9/30 unless other things force me to mix it up.