The "power" of an electric heater is directly proportional to how much electrical power it consumes; if you're in the US then a portable 120VAC space heater is not going to be more than 1,500 watts. The only way to get more heat than that is to use a 240VAC heater or a heat pump.
There are lots of heaters that have a simple mechanical switch that is off and 1,2, or 3 heat levels; that is what you want to use with a smart plug. Just look at Walmart, or Home Depot, or order one from Amazon. Here's one of hundreds:
https://www.amazon.com/Kimviento-Electric-Portable-Bedroom-Bathroom/dp/B09FTM2KTZ
Bear in mind that a Wyze smart plugs, like a lot of other ones, is rated at 15 amps, which is 1,800 watts. But you need to be very careful when using a 1,500 watt heater with a smart plug as it could start to heat up. You need to monitor it closely after it has been running for a while and make sure the plug doesn't feel too hot. Smart plugs have been none to have a melt down when used for very long at that power level.