let me come back.
1. I've tried inexpensive tablet and was not satisfied at all. If you work on a single screen, I found even a small 5x6" Wacom is usefull. And it is not expensive (under $70). Not necessary to have the extra feature (direct access command and menu,...) used for professional work.
2. Trying one in a shop is not really a good idea as you have to accustomized with this special device.
3. Not only you will have the pen in "absolute" mode, but most tablets have also a cordless mouse in "relative" (usual) mode. And you keep your old mouse in use, there is no conflict.