The Mengshi vehicles with ATGM's we have seen all have 4 wheels, not 6 like the one above. This seems to be a modified PCL 171 with ATGM's.
Well, I think the PCL-171's base 6x6 vehicle (CTL181A) is part of the Mengshi family.
However, from memory I don't think we've had many pictures of the Mengshi HJ-10 platform.
A rare pic I recall is this one, which shows the HJ-10 + other ATGM lineup, with the Mengshi HJ-10 platform being third from the bottom, which partially obscures how many wheels it has but looks consistent with a 6x6 vehicle.
More importantly, there is also these models multiple years ago (as part of a display of other CTL181A/Mengshi 6x6 vehicles in use for the 122mm SPH and 122mm MLRS that the PLA since adopted) which is consistent with both By78's picture and also the relevant vehicle in the line up picture I posted above.
... Which is to say that I think By78's picture does indeed depict a 6x6 Mengshi with HJ-10.
The 4x4 HJ-10 carrier vehicle is not Mengshi, but rather based on MV3, and it seems that the MV3 HJ-10 carrier can carry six HJ-10s whereas the Mengshi can only carry four HJ-10s.