How big do i want my pots to be?

If growing in a small ammount of space?

Will 2 litre bottles work?

and can sog be used in soil

yes, people have used 2 litre bottles in an sog set-up... but for an sog set-up the rule is "when seedlings are sprouted in cups, put 4 per square foot.... when they are big enough for a 6 inch container, its 1 plant per square foot", but there are people who squeeze more into less space but i would believe they are experienced with sog and learned the ropes first, not sure.... but if you squeeze more into the 1 plant per square foot set-up, its believed they will yield less.... and yes you can sog in soil....look up more info dude.. or just search for SOG... it had this one thread that really broke it down

Bigger the better, you don't want the roots to get all compacted, if they do there is a higher chance for root rot.

general rule is for every foot you want your plant to grow you should have 1 gallon. so if you figure your final plant will be 3' tall, you want it in a 3 gallon pot.. 5 ' tall a 5 gal pot etc..