The quality settings on your Blu-Ray disc should take maximum advantage of the roughly 22.5 GB usable space on any single BD+R SL disc. The disk-o-meter is not a very reliable indicator. The field above it, where the targe file size appears, can be a better estimate. The actual amount of space needed depends on the format (larger MPEG or more compact AVC) and the bitrate. You generally want the bitrate to be at least as high as the maximum in your source video. If your project is under 2 hours in length, generally you can set the bitrate at 25 mbps and still have a target file size under 22.5 GB, even if working with 1920x1080i files. Above that point, there has to be some trade-off in quality in order to fit everything on a BD+R SL, or else pay $$$ for a BD+R DL.
On standard definition projects, the image quality peaks at about 8 mbps and starts to tank after the bitrate goes below 5mbps. With HD, the best is at 25 mbps. Quality loss starts to appear as the bitrate goes below 17 mbps. It is tolerable, even at a rate as low as 9 mbps, if the scene motion or image complexity is low (talking heads, flowers) and the camera still. Even if your source HD video is relatively low bitrate, you are better off calibrating the output at a higher one, since that entails less recompression or the consequent quality loss. There is not yet any "smart render" in Studio to export without recoding. The competing products that perform this do so only with undoctored clips and the feature suspends the moment the timeline encounters clips with effects. If Studio 13 includes a feature to accommodate multiple video formats, or switch back and forth between recoding and simple transfer, it would fill a big hole.
"Broadcast quality" can mean a number of different things, these days. Since this June, all broadcast or cable channels in the US are digital, but obviously only some are HD. Precisely what type of source video are you editing for BD projects?
The biggest curse of BD projects is that some dedicated players have firmware that is allergic to BD+R or BD+RE. Some won't recognize the menu structures. At times, you can't tell whether the fault is with the disc or the player. The best approach is to burn the first version to a BD+RE, so that in the trial phase you avoid creating an expensive "coaster."
The other curse of BD is that there are relatively few players and so much confusion between real BD players and the conventional DVD players that "upscale to 1080p" and have an HDMI connector. If you distribute work to various viewers, you may have to offer dual BD and DVD versions of the same work, and only the latter gets used. Eventually, distribution of mid-def 1280x720p videos on flash memory cards may overtake optical discs. One can fit a fair amount of reasonable IQ video on a $7.50 4GB SDHC card. That price is cheaper than a typical BD-R "single," even though BD-Rs can be bought in bulk for less, but the SDHC card is re-usable. The disadvantage, though, is that there is no software for creating flash-card videos with menus, yet.