I should mention that there are several devices that will work in place of the Insteon if you want to start looking into those. The higher draw ones are more expensive than the regular residential ones, you’re probably looking at somewhere between 80 and $200 but then you will have direct compatibility with SmartThings.
There’s a Leviton 30 amp device on The official compatibility list which uses zigbee.
https://www.smartthings.com/products/leviton-30-amp-load-control-module
https://store.leviton.com/products/30a-wireless-load-control-module-73a00-3zb?variant=18216462787
A similar Aeotec micro that will handle up to 40 A and uses Z wave. It also cost about half of what the Leviton does.
https://www.amazon.com/Aeon-Labs-White-V3-26-AL001/dp/B00MBIRF5W
A GE heavy duty Switch rated for outdoor use that also uses Z wave. Right now this is only available in the older generation, classic zwave. But GEhas recently brought out a bunch of their other Z wave switch is in the newest generation, Z wave plus, so that might be worth waiting for.
https://www.amazon.com/GE-Appliance-Direct-Wire-Appliances-12726/dp/B00YTCZZF0
And a smartenIT zigbee Relay which is also rated for 30 A. This one is bigger, but also more weatherproof than the small micros.
So several choices if you decide you want to replace the insteon device.
AlSo since you’re new it’s good to know that prices vary a lot and Amazon is not always the least expensive. A lot of times we’ll post Amazon links just because they’re Easy to find, but you still want to shop around. 