Storage/Workspace above garage remodel help

I have this space above my garage and i want to make it usable for storage or light work. I plan on adding lots of insulation, plywood floors and walls for the space in the picture. i estimate needing to support 1000 to 1500 pounds max. Probably a lot less but i want overkill. i would like your great help in determining my options. if i can avoid it i would rather not put load bearing columns in the middle of my garage floor. so that leaves either spanning the 22 foot garage with beams mounted to existing studs in the walls behind the drywall (visible in photo21.jpg) and the opposite wall of the garage or "attaching supports with lags or bolts through roof beams" (visible at the top of photo21.jpg) in effect hanging the floor from the roof. please let me know if i have any other options, or pros cons of existing options. also if i anyone needs any clarifications i apologize for being unfamiliar with common terms. thanks for all your help