ECUMC: You raise a lot of conflicting issues
The reasons you are having these are format, storage media and output.
Format: the file size needed for the various formats is dependent on the resolution (720 X 480, 1920 X 1080, etc.) and the quality MBPS.
Storage Media: if an SD card is used it will be formatted in FAT 32. Maximum file size is 4GB. On reaching that it will close the file and start a new one. You won't see it but you will hear an audio miss for what is lost during the file change.
Output: Roxio does a full render on output whether it to the same format or a different one so you really cannot get around the time factor. IF the output matches the source file it will use Smart Rendering and speed things up. But a general rule of thumb is 1 hour render for a 1 hour source.
As myguggi mentioned, that camcorder is overkill for your needs. Yes it does output in MP4. Also it uses exFAT for the SDXC card which I believe eliminates the 4GB limit...
I suggest you run some tests with your Canon. Set your camcorder quality to that of a SP. You may want to repeat this with LP too. Then record one hour of TV and load it into Roxio to see how it looks to you and file sizes. If you don't have to merge files, you should be able to load your MTS file into MyDVD and create chapters and burn. Likewise the same MTS could be output in VideoWave to make the MP4 or just use Handbrake for that purpose.
Let us know how this works out for you or what stumbling blocks you still have. Your project needs are a little different than what we are used to seeing, so maybe you can teach us a thing or two