Anything above a 10 miles a second would soft ban you if i spoof I usually camp one place and then stay logged for few hours till i go other place BUT BUT
you can remove a soft ban by simply taping on a Pokestop spinning it and exiting repeat this until you get items carefully soft ban means you get no items or Pokemon will run from you after first time of going into Pokeball they will immediately go out and run
Cheers