We play a total of 4 games. Do we add the total points scored of all 4 games to determine the winner (highest wins)?

Say that I used a defensive strategy, where we won with the score being 5-1 (hypothetical). Will I be at a disadvantage against teams that went 21-20 since they have a bigger total score? Or will my team be ahead since the difference of scores between my game was 4, while the difference between the other game was 1?

Seed is determined through a win-loose ratio. The higher the ratio, the higher you rank. Score is only taken into calculation if there is a tie in the Win-Loose ratio. You can see the following on a VexDB page like for example:

This actually shows up in the game manual. Go to pdf pages 19 & 20 (17 & 18 by page numbers) for a full explanation.

Win Points (WPs) determine the rankings. In the case of a tie, APs (Autonomous Points), which are the number of autonomous bonus points a team earns over the course of the tournament, is the first tiebreaker. The second tiebreaker is the number of points scored by the losing alliance in all of a team’s matches, also known as Strength of Schedule Points (SPs).

It doesn’t really make a difference. For each autonomous win, you get four AP. Each autonomous win also gets you 4 autonomous bonus points. Your AP is the number of autonomous wins your team has won, multiplied by four.