ProMods

I'm pretty sure the performance hit comes mainly for the number of driveable roads in ProMods. In SCS's DLCs there usually aren't that many driveable roads available in one scene, even the most complex ones like for example St. Petersburg in the new DLC. Yeah its pretty immense and detailed but it does not have that many driveable roads. In ProMods, there can be dozens of driveable roads in one scene, let's say for example in London. I'm pretty sure that's the biggest performance killer and mainly CPU bound, you need to have a good CPU with high single core performance (ie. new Intels). That said, after 1.32 and 1.33 updates, the performance has become much better, even w. ProMods.

what are you guys complaining about I run ets 2 modded with 30fps no lag and all places in promods work fine ON A INTEL HD INTERGRATED LUL
i5 and 8GB Ram.

it's still very smooth for me.
maybe change your DEF to a lower version and see if that improves fps.