Re: TV-out quality and overscan
What you are probably seeing here is the scaling between the screen that Linux is painting on, and the actual video output.
Unfortunately, the TV-OUT hardware is trying to be "helpful" by defining a "standard" video resolution like 640x480, 800x600 or 1024x768 and then scaling that picture to the actual resolution of the TV format. This introduces effects that are most clearly seen on sharp objects like text.
This was probably invented in the early Windows days when everyone had a "standard" screen resolution and using some arbitrary value like 720x576 would confuse certain programs. I think this is all long history (maybe games are still a problem? I never use games). For the rest of the users, the scaling is just a nuisance. It should go, at least the option should be available to get rid of it.
When you are using NTSC you could at least set the screen size for the TV-OUT screen to 640x480, as this happens to be the NTSC resolution. Probably there will still be scaling, because of the overscan. But it could be better.
For PAL users, I'm afraid there are no options.
I think there exist specialist cards for what you want to do. I.e. geared towards using a PC for broadcast-quality TV output. Those may serve you better.
When your equipment can accept RGB input instead of composite, you could also use the VGA output instead of TV-OUT, with a suitable modeline and maybe via some interface box to convert RGBHV to what your equipment expects.
For overscan, please read the driver README.txt