What firmware version?
What commands did you use for tuning? The hotend can be tuned as a basic heater or as a tool which takes the cooling fan into account which can prevent dips from the cooling fan coming on.
Have you tried tuning heater feed forward? This can help prevent dips when printing fast.
There's no real point in tuning for different temps. Best to use a temperature that is somewhere in the middle of what you would be using. The characteristics of the heater won't change much. Though a 24v bed heater probably takes a while to hit 100c.