Should ankle plates and screws be removed in younger patients even if they cause no problems due to a risk for later fractures or chronic infections?

No: In general, there is very little risk of leaving plates or other hardware in place if there arena symptoms.

Ankle plates/screws: Generally we don't remove ankle plates and screws unless they cause symptoms. Sometimes the screws back out over time or the plates becomes prominent and uncomfortable. If that's the case then removal is recommended but only after union of the fracture is complete.