Are you talking about while driving or stopped. If driving, will your alternator output support an additional 30+ amp @ 13 VDC load?
If while dry camping, you will want to be conserving your batteries, so refrigerator to propane.
As far as whether both devices can be supported at once (while driving), add up the amp or watt load of each and assume that you don't want to run the inverter at over 80% of capacity. Then you can tell US if it will work.
BTW, I can't imagine a standard size crock-pot only taking 150 watts-- the power equivalent of running a big light bulb is not likely to cook much food. Yes, there are some small ones that likely are that wattage.
