So a convicted felon can lose their right to vote, but they can still be President. Gottit.

Who can vote is a decision for each state (subject to various federal restrictions added over time, mostly in the form of Constitutional amendments), who can hold the office of President is determined by the Constitution.

Pence being a spineless coward aside, it depends on what he is convicted of. Trump has been charged with a lot of shit, and some of those charges would not disqualify him from the Presidency while others would.