I have a Pseudemys Nelsonii and it's one of the friendliest turtles ever. I have RESs also and I do not keep my cooter with the RES, The sliders are more aggressive and often harass the cooter.
The care if very similar to sliders, but requires much, MUCH more vegetation. Often my cooter will ignore live prey or pieces of fish and go for veggies. Most cooters get bigger than sliders, so down the road, you'll need a little pond or a big tank (75 gallons minimum for the bigger species).
Cheers,
JJ