If you're just recording locally to add it to sony vegas, then here are the recommended settings for 720p 30fps:
Encoding settings:
CBR off
8000 bitrate/buffer
AAC (any bitrate you want)
Video settings:
1280x720 base resolution
Downscale off
30 fps
Advanced:
In "custom x264 settings", add "crf=18" (without quotes)
Enable CFR (Important for vegas, along with using AAC encoding. Note, don't confuse this with the "crf" above, that's different)
That should give you great video that's most likely more than enough.