Use Ryzen master to monitor temperatures.
What you are seeing is an individual core spiking in temperature as windows cycles through the cores doing background tasks. Nothing at all to worry about.
Minimum temperature is going to depend mostly on ambient temperature and case airflow.
If your case airflow is sufficient then your minimum temperatures will be around 15C above ambient temperature.
The Ryzen 3000 chips throttle at 95C and run with a target temperature of 75C.
Anything below 95C is ok, anything under 75C while under load is excellent.