So... umm about D2:R graphics

I dunno where to ask this question since we don’t have a dedicated D2:R forum here on EU side but:

Will D2:R be able to run smoothly on an average PC if during gameplay it is always in the classic mode?
Or does the classic and modern graphics run at the same time, while only one of them is visible but both data runs through the CPU and/or GPU therefore the game runs the same no matter which graphics are currently visible?

I ask this because my desktop PC can run D2:R, the family laptop probably would struggle with the modern graphics since it doesn’t even have a dedicated GPU, so I thought if the graphics would be set to classic on the laptop all the time, it may not struggle but it depends on the games coding how it handles the two graphical layers, so does anyone have a clue?