This video shows the biggest changes to take note of with the introduction of the new World Handicap System in 2020.
0:25 - New Handicap Index Calculation
2:15 - New Course Handicap Calculation
4:45 - New way to determine Max Score on a hole
Here is a condensed slide show from GAP with more information on how the new WHS is being implemented.
Slide 1 shows the new Course Handicap calculation, including course rating and par.
Slide 2 shows that Course Handicap could change a little or a lot in the new system. When the rating for a set of tees is much different than par, you'll see a bigger difference. The biggest difference you'll note is how the yellow tees are affected. The new system eliminates the need for rule 3-5 to calculate strokes given, all you need is the new equation.
Slides 3/4 explain Playing Handicap. This is if you are playing in a tourney where a Handicap Allowance is in play, for instance "50% of Handicap" or "90% of Handicap."
Slide 5 shows the calculation for your max score on a hole, which is Net Double Bogey. To calculate, you add par + 2 (double bogey) + however many strokes you were getting on that hole. The video above has a detailed explanation of this around the 4:45 mark.