How should White play 33 here?
You have just rolled a great number, and now you just need to play it well.
Even if you cannot Pipcount, having 3 checkers back compared to your opponent having only 1 checker back, you must be behind in the race.
If you are behind in the race, your main game plan should be priming. Therefore, when you are comparing the different alternatives, you should select the move that gives you the best priming game.
You consider making the most number of points on your side of the board by playing 8/5 13/10 6/3(2):
This is not a great priming structure as the 10 point and 3 point can never be part of the same continuous prime unless you find yourself playing with 16 checkers.
You consider 8/5 13/10 24/21(2):
Making an advanced anchor looks nice, but it is pursuing the wrong game plan. You really want to be creating the best priming game you can and making the 21 point is the wrong goal.
Consider 8/5 24/21 6/3(2):
Your 8 point and 3 point can be part of the same prime, but there is no need to play 24/21. By playing 24/21 you may need to make it next turn to protect against being attacked, and you have given your opponent rolls that will attack and make their 4 point.
When you are comparing primes, the best primes are continuous primes i.e., primes without gaps on them. Consider 8/5 13/7 10/7:
You have made a continuous 4 prime and your back checkers are on lower points which are less desirable for your opponent to make.
Once you have your 4 prime in place, you can extend it, escape checkers into the outfield or make an advanced anchor.
After this play, you are almost a 50-50 favourite.
Your gameplan is priming and continuous primes are great primes.