The front squat primarily works the quads and that is the point' although all upper leg muscles are involved. I wouldn't worry about 'how much hams are involved' because if you choose to do FS then you obviously want to work the quads more!
On any squat variation the deeper you descend the more your glutes and hams are involved.
Foot pressure will also influence the muscles you work, with pressure exerted through the ball of the foot primarily activating more quads' and pressure exerted through the heel activating more glutes and hams.
The degree to which the hams are involved compared to the quads will have a lot to do with 'your' technique and 'your' body structure, which can't be ascertained here.
So unless you are involved in some EMG study thing I wouldnt even bother worrying about it!