Hey California regs are very strict and controlled nothing like Hawaii. You will have to read the regulations thoroughly to understand them and not break them. The game wardens will cite you a ticket here and they do check on people. For a pdf of the regs check out here:
https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=42130&inline=true
This link will show pictures of game fish by type and also habitat:
California Marine Sportfish Identification
Milton Love I believe has some good books on fish ID but I am sure an amazon search will help.
You will not be able to drag a diver down flag when you dive here for the most part as the kelp is thick. Its like diving in a hapu'u forest. Stuff is growing everywhere. If you go blue water then you could use a flag, if you go out on a boat or kayak then you should use a flag.
It sounds like you have the gear I would just read the regulations over and over again.
Another resourse that helped me when I moved to California on Fish ID is this one here:
California Fish [Pier Fishing in California]
good luck