1. [zoom in while recording] Sony's able to do so but not Canon's. what i can say it's depends on ur judgement and eyes when it comes to focusing in shooting video and a lil help of the function "Peaking" u'll need Magic Lantern for Canon
2. S-LOGII is from Sony, canon' is C-LOG, and V-LOG from Panasonic, pls go google and read, it will be more detail. Same as CODEC, but most DSLR are using H.264, bitrates is one of the factor as well.
3. go watch a lot [i know this doesnt really helping in answering ur question] coz there are no one channel which cover everything, perhaps youtube: DSLRguide is a good place for u to start with

This post has been edited by jerren: Sep 8 2016, 07:40 PM