Yes. Walking, Nordic Walking, Running and Hiking show Pace, in minutes per kilometre. Cycling and all other activities show Speed, in km/h. You can change the unit for each activity.
The choice applies to all routes of that activity, in Statistics and in Estimate. It syncs to your other devices through iCloud. To return to the activity's usual unit, choose it again.
TrailRunner shows distances in kilometres or miles, depending on your device's region. To change this, open your device's Language & Region settings and set Measurement System. Pace and speed are always per kilometre.
Choosing pace or speed only changes the display. Nothing in your routes is converted or rewritten. You can switch back and forth as often as you like.