Most 147's in NZ are 2.0l TS but there are some 1.6's. Selespeed only comes with 2.0l. There is also the GTA but this is 3.2l V6 and somewhat different.
Selespeed is a ordinary manual gearbox that has the gear changes "robotised" so you don't have to operate the clutch or gearlever. Clever electronics and an electro-hydraulic actuator do it all for you. The hydraulic actuator can fail and this can be expensive to repair/replace. Makes no difference if in city mode or you use the paddles. Some people don't like Selespeed but I enjoy it and mine hasn't given any trouble at all.
Trim levels don't mean a lot just look out for the spec you want - leather and Bose are the things most people like. But cloth and the std audio are fine.
What to look out for? Well you need to know the status of the cambelt and associated tensioner/idlers - they should be changed every 60,000km and it's fairly expensive. Ideally go for a car which has just had this done. Generally, NZ new or ex Japan are fine, but Singapore cars can be trouble.
Hope that helps