Since Rhus aromatica is well known to be allelopathic, I would absolutely assume (rightly or wrongly) that the cultivars would also contain the same properties.

However! Here's where the research gets pretty thin.....not all plants are sensitive to the allelopathic chemicals present in any particular plant. Your job will be to see if there is any documentation linking the suppressive chemicals in Rhus to the specific plant genera that you are interested in keeping healthy.

Remember, even the well known and much researched Juglone isn't a problem at all for most other plants.

I hope that I've explained it in a way that makes sense. Be sure to let me know.