Hello and welcome to the forum. You have quite a list there of needs and wants. I know it is frustrating and you will still have to play around to find what is going to work best for you.
For pocket size and battery life I am going to suggest any of the eGo kits or eGo pass throughs. The eGo battery will allow you to test out different type of atomizers and hopefully help you find the one that will work for your best. This battery has a 510 connection.
For your cartomizer or atomizers needs I am going to suggest the Boge standard and low resistance (LR) cartomizers. The LR's will simulate vaping at a higher voltage. The vapor will be warmer, more throat hit and it can kill the flavor a bit.
I am not a menthol user, so I really can't help you there. I have tested a few different menthol flavors and my favorite is the Vapor Talk Mentha. Menthol flavors will give you a pretty good throat hit. If that is something you would like to avoid, I suggest picking up a couple different flavors to try out.
You can find the Cartomizers and Mentha in the the Vapor Talk store and the eGo kits/pass through in the Forever Vapor store. There is a 15% discount running for the holiday weekend.
We also have a list of supporting suppliers on the front page. They are all reputable and have quality customer service.
The other part that will affect your throat hit is the nic strength. The lower the nic strength the less of a throat hit.
Good luck. Making the switch is a learning process. Battery life is the key. The eGo is your best bet for battery life and small size. Like I said before it will allow you to experiment with the different types of 510 atomizers, 510 cartomizers and the eGo tanks to fit your lifestyle.