Caveat lector: I am neither an engineer nor engine builder. I just read a lot.
You have received correct descriptions of static CR. But you framed the question with concerns about preignition and how it is effected by under- or over- square configurations and fuel quality. Unfortunately no one is going to be able to answer the questions to your satisfaction.
Most people point to calculated static CR as an indicator of fuel requirements and an engine's propensity to ping, knock, rattle itself to death. That is a rule of thumb that used to be true for most applications. Engines are not the same now as they were back in the day. Much more is known about air flow and fuel dispersal and how to control it. There are programs available to give a graphic indication of the swirls and eddies and paths of an air charge and the propagation of the flame front under dynamic conditions.
My Fiesta ST makes 190 HP with 1.6L and a turbocharger. With a mild tune to the ECU and no other changes it will make over 200 HP. With only bolt-on modifications it will make over 240 HP. Determined tuners are achieving more than 300 HP with major changes. The EcoTech 1.6 has a static CR of 10.5:1.
Just a decade ago Top Fuel engines were making 1000 HP per cylinder. Today the mark to beat is 1388 HP per cylinder. That mind boggling HP level is achieved with a static CR of 6.5:1.
There is no way to say flatly that a specific static CR will cause x, y, or z. You need more information to have an idea of the personality of the engine. I have read about tuner built Honda engines that are streetable with a calculated static CR of 16:1.
Beside static CR there is also dynamic CR. While the static CR can be determined with measurements of the volumes at TDC and BDC, dynamic CR requires knowledge of several other measurements. Valve timing and piston speed are perhaps the most dominant determinants of dynamic CR. But there others; including temperature and barometric pressure.
Even a discussion of preignition in over- or under- square engines has to include more than bore and stroke. How long are the rods? What is the quench clearance? Domed pistons? Maximum piston speed? Combustion chamber shape? Position of the spark plug? Multivalve? Reversion and scavenging characteristics of the exhaust stream? Length of the intake runners?
To better understand preignition and the relationships of valve timing, ignition timing, A/F ratios, piston and dome shapes, VE, BSFC, pressure pulses, scavenging, and on and on, read everything you can find on the subject. I am especially fond of articles written by The Old One. Just Google theoldone. Energy Dynamics is the very first return. But I warn you, for a gearhead that site is a candy shop.