i've gone through these m4v versions of the tapes and pulled out the clips that i want, but no matter how high a quality i try to export them with, the quality goes way down - both frame rate and resolution goes way down.
What rendering settings are you using, exactly? Among other things, the theora video codec has a quality setting of 16 by default, which is very low, you want to raise it (the maximum is 63 or something like that!).
the sound stays ok but it adds this mysterious clicking.
I'm guessing you are using the stable 0.13.3 release; see the user manual in the troubleshooting section near page 11, I'm guessing you're affected by the crackling noise problem due to the sample rate (which has a workaround).
1. can i take clips out of a file without changing anything else? just exporting those clips exactly as the originals?
Maybe with avidemux... but lossless processing is currently not possible with pitivi.
Strictly theoretically speaking no, because you are not using lossless codecs, you are re-encoding, applying transformations to the image (well, if we had effects and transitions ;), etc. Unless you use avidemux and apply no filters at all, for example.
2. can i retain the same quality in the final project as i have in the clips?