The pie doesn't change, and not only does the pie remain the same, but other people's pies don't magically grow while the one pie gets smaller.
Here's some math:
120mv hypothetically control 60% of the total stake.
If they are limited to 10 votes each, or 1:
3 account worth 40mv with 10 votes each will have the exact same 60% control and be able to distribute that 60% control over the top 30 witnesses, or 30 accounts each will have 1 vote each and they will still have exactly the same amount of vests and total 60% of all the vests to distribute over the top 30 witnesses as before.