All Secrets are found in the first 4 minutes and are marked on screen, the rest of the video is just finishing the level and yapping.
First time making a live commentary guide, let me know if you have any questions and I will do my best to help. I have yet to see another person make guides for the latest updates that have added a few new secrets in a couple of levels, I will Upload an easy guide for chapter 2 tomorrow.
UPDATE- On the 22nd the devs updated the map again to add back 2 secrets that were in the previous version of the map.
They are both in the Subway Portion and aren't too hard to find, the first one is just after going up the stairs from the platform, on the right hand side of the room there is cash hidden behind a bench.
The 2nd secret is behind the cigarette advertisement I opened before opening the gate to exit the subway, there is some cash here you can also grab.
Also worth noting one of the sewer secret locations is slightly further down than it was in the video, but shouldn't be hard to find.
I may make an updated guide soon, but I suspect there may be more updates that will further change these secrets so I will wait a while.