Assuming only 8 players are protected like the last time the NBA expanded in 2004 with the Charlotte Bobcats, then the obvious 8 players to protect would be:
1. Wemby
2. Castle
3. Harper
4. Keldon
5. Champ
6. Vassell
7. Kornet
8. Bryant
You don't protect Fox in that situation because there's almost zero chance that an expansion franchise would want to pay 30+ year-old De'Aaron Fox the remaining 3-years/$174M remaining on his contract. So you'd basically give yourself another player to protect in that situation.
Worst case scenario, an expansion franchise does pluck Fox for whatever reason and suddenly you have that contract off the books at a time where you just gave Wemby a Max Extension and extended or are about to extend Champagnie, Castle, and Keldon. You let Fox walk and then Harper slides right into that starting PG position in 2028. Bada bing bada boom.
Edit*: Only way I might change my opinion on this is if we ring within the next 2 years and Fox plays well while doing so. In that case, you'd let 32 year-old Kornet go unprotected.