Part one. working units. Well yees and no. More no. Maya actually does act* as if no units existed and that the working units oprion is nothing. So no matter what you think thet unit thing does IF you want to use imperial units do not ever set units to even inch. Cm is only safe.
Since maya dont act ob the unit settings trough the ENTIRE spectum of how maya works, its not safe to put them into ANY other attribute than cm. So never ever set thet value to anything.
Units dont exist in maya, mainly because everything is relative. you can set the physics constants in maya so any uinit can be any other unit. In camare work and rendering units have no actual impact on anything. Only simulation framework is affected. And this by the way applies to any computer program, there just si no reference to credibly say units are there. No reference no units, the only thing thet matters is whta the USER thinks they are.
And its set to work in faux meters, that is it assumes by defulta everything is meters.
SO setting units has no useful, or sane end result. Thus never set them.
* Only how it acts counts.
PS: i think thi particular thing would benefit form text trascryption as its much fastter to find relevant info in text based medium without wasting 2 hours to rechek something you missed. Any pweson who can read can find what hes looking for in 30 page thing by glancing in about 10 seconds. So having text by side would be usefull, and bookmark sections in the video for searching.
PPS: I wont bore myself by watching the rest