Of course this is up to taste, but most people will enjoy the leveling experience as well as creating alts. Don't force the leveling experience to be too slow. Otherwise people have the option to pause XP on character portrait.
Keep rested XP as 2x XP & give Warmode +10% XP boost (middle ground between 5% and 20%).
Slightly faster leveling just means we can do more of what this amazing slow game offers (twinking, challenges, L1L, endgame etc.).