Ehlers will be fine when he fills out more, he went from 163 or 165 to 176 at the combine, he put on 13 lbs in 10 months, I'm going to go ahead and guess he'll end up somewhere near his dad and brother at 190 lbs with that sort of progress.
I'd also suggest you actually watch Ehlers play, hes not afraid to use what hes got, Ehlers at 190 lbs scares me. He doesnt care about getting big hits, we saw it in playoffs too, he just got up and leveled a guy the next shift, you're vastly underestimating Ehlers if you think he's light. He sure doesnt play light.