Whenever I play on modern organs (especially built in the Neo-Baroque style), one of the most common defects is harsh mixtures which are very painful to people with hearing aid.
Should you follow strictly composer's suggestions about using mixtures or should you be mindful of how it sounds?
Of course, the real result out in the nave is what matters, not what stops you use.
Often Principal chorus (Organo Pleno) registration where you normally would play with mixtures is sufficient on 8', 4', and 2' principals, especially when the building is not very reverberate.
I recommend avoiding such mixtures or using them very sparingly, perhaps only in a couple of culminations.
PS The same goes with difficult to play couplers on certain mechanical action organs.