Cardio, elliptical, and toning my back

Is it ok for what?

Squats and deadlifts!!

Yes, I have a rowing machine (water rower one) it's a great alternative to the Elliptical and works upper body and core! I don't use the Elliptical, I cheat too much on that sucker!

Erectors: Back extension
Obliques: Side oblique crunches on back extension station or roman chair.
for traps, lats, rear delts and all of our other friends back there good old fashion hard work with them there heavy metal thingy's

Muscle seperation, striation, and other asthetically pleasing attributes that make a physique purtty come with time and lower levels of body fat compostion. Oh yes, if you canfind one a versa climber machine is the gold standard of back chiseling cardio equipment. Many gyms do not have them because they are considered torture devices when used properly. I wish you the best in your journey to the back you desire. And do not ever ever ever, use weight when training obliques as this will make them bigger. I like it myself, but most women I talk to say that is the last thing they want personally. I like my big muscular obliques, and so does my wife.