I think the videos make some good points. Yes, gangs will be a problem. I also think you have to look at the real world and see how things like that have been handled.
During the LA riots Koreans banded together and kept the "gangs" at bay at least in their area.
During Katrina, most people that stayed (didn't evacuate) banded together to protect their neighborhoods. This kept looter and gangs away. I think that most communities will band together at least initially.
During the Detroit riots, surrounding communities set up road blocks and curfews to prevent gangs/looters from spilling into their communities. Containment will be one of the first things that happens. That can be by the police and/or physical barriers and/or national guard.
Also the first things gangs are going to do is go on the defensive to protect their turf. Once they have security they go after easy targets. They will hit the stores first, the weak and elderly second and their own neighborhoods. It will only be until they expend the resources in their own areas will they start roaming looking for targets of opportunity. They will not be likely to want fight on unfamiliar ground. Remember too that they have to protect their turf from other gangs as well.
Of course this presupposes a scenario of total governmental breakdown which is not likely to happen. Even if the feds breaks down their will still be state, regional, county, and local control. I served on a regional emergency management board before I retired. There are pretty thorough emergency plans in place in most areas.
Also from personal/community defensive standpoint you want to set up concentric rings of defense. Protect the area first by defending the main routes of access and egress. Protect the community next, then the subdivision, then block by block, then house by house. Nobody but a well disciplined, trained military force with a lot of people is going to be able to breach all the defenses without terrible casualties.
"It does not take a majority to prevail... but rather an irate, tireless minority, keen on setting brushfires of freedom in the minds of men. " -- Samuel Adams