Compression ratio doesn't determine boost. The method you use to control boost determines this. If you run without any boost controller, this is adjusted by changing the wastegate actuator. For low boost and a small quick spooling turbo this is probably just fine. You can do this together with a manual boost controller to make small adjustments, depending on how you're tuning the car. Generally though, the wastegate actuator determines boost.
If you go electronic, then you can program a set boost level.
For a given goal on power, you need a certain amount of air, and a certain amount of boost. Eventually you just HAVE to run a lower compression ratio because of preignition or you can't keep the combustion process from spilling over into the exhaust (which doesn't power the car). I can't imagine you could get away with something like 1bar on the stock compression ratio. If it didn't preignite, you'd never be able to run enough timing. Your timing would be pulled back so far your gas and air would just be burning in the exhaust, not in the cylinder, doing you no good. Say, you could up from 12psi to 15psi, you'd find out you had to pull timing another 3 degrees to avoid detonation, but then that extra 3psi worth of air might just be cooking your exhaust manifold and exhaust valve rather than pushing the piston. You'd just hit a ceiling and either destroy parts or just have to back down.