To answer the second part of your question, running low compression and high boost vs. high compression and low(or no) boost makes more power due to consumption vs. efficiency. With higher compression you increase the efficiency of the combustion process releasing more power from the same amount of air/fuel. Say you have a car with 11-1 compression and you increase it to 12.5(about the maximum for gasoline) and you see 40 hp gain. You made the engine ~14% more efficient. Now when you lower the compression to decrease the chance of knock to accommodate boost you allow yourself to run like +20psi(assuming your block and rods don't blow and all other things)so while the N/a horsepower would be lower because the reduced compression makes it less efficient so lets say like 255 whp, you are consuming over twice as much air and fuel so double that plus some(about 14.7psi atmospheric so you'd be at about 1.2bar) and you'd be seeing about 566hp. 9-1 compression correctly setup and tuned can go to over 35psi so around the 862hp mark. of course those are hypothetical hp numbers but you can see the point that while you increase efficiency with higher compression, you can burn a hell of a lot more fuel/air with lower compression and boost.
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