B, re: question #1, successful SV cooking requires a partial change in the way you think about your cooking because of the cooking environment and the lower temperatures employed. In conventional cooking you have been thinking about mass, now it's thickness the effects cook time.
Think about your two pieces of steak and what you are about to do to them.
Imagine a race between equal amounts of heat energy penetrating your two steaks. Which steak gets the heat at its centre first?
The steak with the shortest distance to its centre.
That's why you let thickness be your guide to timing.
A ruler always beats a scale in planning your successful SV cooks.