It is usually not so much that you can use RCA/XLR outputs as it is an issue when you try to switch between RCA/XLR inputs on something like an amp--using one from one source and the other from another source and doing the switching at the amp. The two share some of the same circuits and you can do serious harm somewhere.
To answer your question I am unaware of any equipment that has problems using both outputs. You can probably try it and see if it can work and more important---do the mismatched signals (XLR is usually more decibels) conflict with each other in your listening environment.
To answer your question I am unaware of any equipment that has problems using both outputs. You can probably try it and see if it can work and more important---do the mismatched signals (XLR is usually more decibels) conflict with each other in your listening environment.