Jointer or hand plane would be ideal to flatten warped boards. A tablesaw can be dangerous if you don't have at least one completely flat side. You can make jigs for the tablesaw. Similar jigs can be used for thickness planers. I even have a jig that allows for a plunge router to be used.
I agree when it comes to moisture content. I have a moisture meter at home and I won't use any lumber that's above 15% with the exception being treated lumber. Also, keep an eye on moisture content in the train room, I need a dehumidifier in the warmer months.