I don't know which type of adsense ads has better CTR, one of my new site got 432 visit but only 7 clicks....CTR is only 1.62%, can you plz give me your experience? thx..

That's a pretty good ctr... it depends what the niche is, site layout, etc... CTR is weird, you want it to be high, but too high and google gets suspicious.

If you choose the bigger areas, sometimes you get links and sometimes rich media. I always make my the text links look like the site links so people are more likely to click. (change colors to match) google actually reccomends that, but like I said, too high of a CTR and you could get flagged. I think I read somewhere on a post here someone made the ads look just like google asked, and they suspended his account until he made them look different. Really odd.... but it hasn't happened to me yet.

normally i prefer text ads is more better than image ads

I split tested for about 3 months and no only go with text ads. However I also have a good amount of image ads out there, just not with adsense