Curves will steer differently due to one being a drawn implement and one being mounted. The guidance system's goal is to put the implement in the right spot so having different mount styles will change how it drives the curve. 


Yes you can drive boundaries and such with a UTV and do fine, many do it here. You can get into the fields when it's too wet to do other stuff. 
Most here have gone to using boundary track guidance lines on the JD stuff which is possible on anything newer than your 2630. You have a boundary and it makes the guidance line all the way around for you, no driving and saving all the curves