Your all over the place, I think it may be why people are voting you down.
I think it's great you understand there's a bunch of different codecs, keeping the all updated, and yet productive and not conflicting can be a harsh balancing act. The number one rule if your going to debug everything on a production box, is you keep a cloned backup before you start.
As far as browsers go there's two things. Keeping them secured, and them actually being productive. e.g. you can view the target content . There's no law saying you can't make your own plug-in as well.
As far as codec's go, it's like hurding cats, from free to commercial professional codecs, project to product there's no written rule. some codec's do register system wide. Basically what it comes down to is is what your trying to produce, or target you do whatever it takes to get it done. The more you know about operating systems and such the better off your going to be to find and debug problems when they crop up.
note: problems will crop up, and you will have to debug them yourself--without google as a crutch. The good news is you'll feel like a god afterward.
I think AVCHD is more of a pain in the butt (a different set of problems) than MPEG-LA but I am looking at it from a different point.
I don't like the idea of MPEG-LA being a time bomb for the successful producer. note carefully I didn't say it isn't right for them to try to do it. After all they own it. All of us on Earth have had enough economic damage already. I think ultimately the old ways are going to have to be thrown out, or freed up. This MPEG-LA thing is a symptom of the insatiable greed and corruption which is now starting to bite us all collectively in the ass.