Am assuming you're looking at all single-phase motors. Here are a couple links that might be useful to you:
https://chintglobal.com/blog/soft-starter-working-principle-applications/
https://www.baldor.com/Shared/manuals/834-602.pdf
Some low-cost options here:
https://www.automationdirect.com/adc/overview/catalog/drives_-a-_soft_starters/ac_motor_soft_starters
I've never used a soft start on a single phase motor - just on 3-phase motors for work stuff. And I've given up on soft starts for 3-phase motors now that there are so many VFD options.
My opinion - Fridges and freezers don't really benefit and may not start with a soft-start device. Air conditioning devices may be a different situation depending on how they're designed/built. My external AC compressor/fan unit seems to have its own soft-starter built in. Others will know more.