Hi, with my RX (Gen 5) to disable the speed warning for each trip involves the following:
1. Tap Vehicle icon
2. Tap Driving Assist
3. Swipe screen left then press Customise
4. Tap Notification
5. Tap Excess Speed Notification
6. Choose Off, Visual or Audible and Visual (the default) - I choose Visual only
7. Tap OK
….then drive 😂
In answer to your second question, no Sport mode doesn’t automatically disable the beeps in my car, but you can drive in Sports mode on pure EV.
Hope this helps