i use a seperate 3s lipo and standard lawmate regulator. never had any interference. 420 rmrc 12v cam and 500mw 2.4 Lm tx
you can say what you want about extra batts being a weak point or whatever but to me it is so much cheaper and easier than trying to filter and troubleshoot interference in the system when running off the flight batts.
i dont even use shielded wire at the moment LOL not a single ferrite ring or filter in my video circuit. no interference to speak of.