I use 3440x1440 at 125%.
Compared to DO11 the scaling of large icons is too large and of the small too small. And iconsets with 32x32 are shown as 40x40 in prefs.
Icon sets which do not specify DPI (i.e. all ones made before Opus 12) will be scaled to your DPI.
So if you were using a larger icon set before to compensate for the lack of DPI scaling, its larger source images will now be scaled as well, resulting in something larger than you probably want.
Icon sets can specify how (and if/when) their icons are scaled for different DPIs. See the Icon Sets section at the end of the Opus 12 release notes. (Last two pages in the PDF, currently.)