The usual extra info...
There are 54 events (52 Trophy + 2 TT) and the rewards 25-50-75-100% are split 10-16-21-33GC.  You will need both cars to complete the whole series, but if you've decided to wait and go for just the standard Chiron in its LTS (PR88.6 required) you'll still be able to reach 75%:

(Obviously I used the Sport for illustration purposes! )