Okay, this may ramble a bit.
Small f numbers mean a bigger hole for the light to pass through, so you can use faster shutter speeds or lower ISO's for the same exposure. They also let the cameras autofocus work more easily and accurately as there's more light for them to work with. Not sure what you mean by "how the different aspects of the lens interact", can you be more specific?
It also means a shallower depth of field, so at f2.8 little is in focus, at f8, much more is in focus. Much beyond f13, you may start to get unwanted diffraction effects, but thats a different ball game altogether.
Adaptors may allow other lenses to be used, but you may not get full functionality (autofocusing metering etc). I'd look at 50mm f1.8 primes, as the bang for your buck you get with these lenses are unbeatable.
All lenses are different, some may be better than others, but they have been designed to work with a specific camera mount, so they expect the sensor to be in a certain position behind the mount. Using them on a 4/3rds body will give a crop factor of about 2, so your 50mm prime on your 4/3rds sensor will give you the same image as a 100mm lens on a full frame sensor.
The other rule of thumb is that a prime lens will give you a far sharper image at the same f numbers than a zoom at the same focal length unless you drop a fortune on pro zoom glass, and even then my 50mm f1.8 beats my 15x as expensive 24-70 f2.8 at 50mm at most apertures, and it goes to a wider aperture…
Hope that helps a little.