When working with a lender that offers a VRM product, your payment will remain static on the day of closing, meaning your VRM payment will not change & only the principal & interest on the back end will fluctuate with any BoC change. This means your amortization will otherwise adjust accordingly.
When the interest rate drops, your amortization drops. When the interest rate pops, your amortization pops.
With some static variable rate mortgage products, there is a trigger rate and trigger point which will inflict an increase to your payment should your mortgage ever reach that point (see below for explanation).
It’s also important to note that not every lender that offers a VRM product, or has the trigger rate / trigger point policy.