26 and 29 ride differently, but both are great at what they do and neither one is better than the other. It's just personal preference. I like the 29er because it puts me up higher for better visibility and ability to roll over stuff like roots. They climb well. 26ers are more nimble and turn faster. 29ers can turn corners well, you just have to get used to it's different cornering.

Fork, fork and fork. Better the fork, the more comfortable you can make the ride and adjust to your surroundings. You want one that you can adjust the rebound (how fast you bounce back up) and the suspension. The lower end models usually have Suntour forks. They are heavy and have minimal adjustments. My understanding is that air forks are better than coil. I've never owned a fork with air so I wouldn't know. Obviously you don't need to start out with a TOL fork, just something mid range. I think the Recon is the start of the better forks out there.