Topaz 4 Using both iris2 and nyx 2 together or step by step?

Is it better to use iris 2 and nyx 2 in one operation with the “second enhancement” function or is it better to use them one after the other in two runs? Does the order in which I use iris 2 first and then nyx 2 or vice versa possibly also play a role, especially when upscaling?

It should be best to use nyx as the first enhancement and Iris as the second enhancement.
My general advice is that the AI models work better on cleaner sources. Nyx is made to clean videos. You’ll have to judge if it does a good job. (Nyx 2 oversharpens everything I run it on.)
Enabling the second enhancement should get you the exact same result as running one, and then running the other on the results of the first.