Do a grill first. I vote for ribeyes, but burgers are good, too. With steaks, you can play around with hot and cool zones, by loading your hot coals on one half of the grill. You can do the same thing with burgers, or chicken parts.
Low and slow on an OTG takes some practice. Go low risk at first, and ease into the more complicated cooks, IMO. You and your OTG need to get to know each other. Weber kettles are great cookers, but they don't do magic. You still have to learn how to use them. Keep it simple at first.
With a kettle, I think you should grill first, and smoke once you get the grilling down. Just my two-cents.