Controlling Home Assistant devices through Smartthings was not as easy as the other way around with that integration. It is possible though using virtual switches. If you create virtual switches in Smartthings, those will show up in Home Assistant, and then you can write automations on either side that trigger different devices off of those. Keeping their status (ie on vs off) in sync was a bit of a problem though.
I also had used Node Red and webcore together, but not sure if webcore is worth investing too much time in since it is Groovy based and likely will not last much longer