Re: 2 or 4-stroke
It really is a personal choice.
First of all, there still isn't a 4 stroke engine that mounts to your frame. The two stroke bike engine was cast to fit a bike frame with built in clutch. Fit being a loose term seeing just how many types of bikes people around the world strapped the chicom girl too. And despite her earned reputation of grenading, the leetle beast can be made to be more reliable. The 4 stroke sits on a platform of some type.
You simply will get more power to the ground, quickly with a well tuned 2-stroke. Don't care what anyone says, a 4 stroke 49cc engine is not a crotch rocket. They do absolutely great for what they are, but then again no manual clutch built in is a bugger too. Some better gear box choices than there used to be for 4 stroke, but nothing fully mature.
Probably read the forums for a few months to get some better advice. I'm just rambling....