Not measurably. The overwhelming majority of latency is driven by internet traffic routing and switching and that tends to be stable at about 20ms, plus the locally variable radio frequency aspects of VM's networks, which adds the yellow fringe on a BQM.
Normally latency (lag) problems are on the VM RF side of things. All that modem mode does is to bypass the hub's built in (and under-powered router) with a competent product you've provided yourself. Usually gets you a more capable router and better wifi, possibly gives the hub's CPU more time for DOCSIS signal processing, but you'd not expect to see a measurable change in latency.