The narrow 2WD front tires will not fit on the Tamiya brand 4WD front rims or any other brand front rim (such as Losi 4WD front or J-Concept Rulux 4WD fronts).
The width is basically the same between all brands of 4WD front wheels for 1/10th scale buggies.. Even if the Tamiya wheels look a little leaner, it will still mount all 4WD front tires perfectly..
I have used Tamiya 4WD fronts, Losi 4WD fronts and J-Concept Rulux 4WD front wheels on my DB-01. None of them will accept 2WD front tires correctly..
The wider 4WD front tires are necessary for 4WD traction
All you need to do is select the right tire tread and compound (softness / hardness) for the track surface you are running on..