If your ONLY use for the joined output files is playing (no additional editing required), there are some streaming options, that you might want to look into:
WMV (Windows-based) files, with a lowered Bit-Rate
DivX (X-platform) files, with a lowered Bit-Rate
AVCHD H.264 (X-platform) files, with a lowered Bit-Rate
When outputting, the two determining factors for File Size are - Duration (fixed by the combined Duration of the Source Files) and Bit-Rate. As Bit-Rate goes down, so does quality. However, some CODEC's allow for lower Bit-Rate, with minimal quality loss. The ones above do a good job there - the Bit-Rate can be lowered, but visual quality stays pretty high. Finding the ultimate Bit-Rate for smaller File Sizes and adequate visual quality, is a balancing act - lower the Bit-Rate too much (smaller files), and the visual quality suffers. Improve visual quality, and the File Size goes up.
It appears that you have found a balance, that is acceptable to you, if I read correctly. If so, well-done.
Now, if you plan on re-editing the output files, at a later date, there are more considerations to be taken into account, and to maintain quality there, the File Sizes WILL be large.
Thanks Hunt, yes, I'm very happy with where I landed. I was also looking for maximum compatibility now and in the future, and felt, correctly or not, that MP4s would be recognized by multiple platforms as long as anything else.
For compatibility, I think that the MP4's will be around for a very long time.
Right now, it's extremely popular, and very useful. A newer CODEC, H.265, is on the way, but will probably take quiet a while, before it displaces MP4 in popularity. Even if MP4 falls back a bit, it will still be around.
Good luck, and glad that you have found a good output - that "balancing act" can be tough, but you have mastered it.