The fastest strategy for the 71-lap Austrian Grand Prix is a one-stopper. The quickest way is to start on the P Zero red soft tyre for 24 to 28 laps, before switching to the P Zero White hard until the flag. Alternatively, start on the P Zero Yellow medium tyre for 27 to 32 laps, before finishing the race on hard. These two strategies have a more or less identical total race time, but the latter offers slightly more flexibility.
The second-quickest strategy is to start on the soft for 30 to 34 laps, then go on medium to the end.
A two-stop strategy is definitely slower, but it would go like this: two stints on the soft tyre of 16 to 18 laps each, then finish the race on either the medium or the hard compound (depending on how things were looking at that point).