All the relays require about the same amount of work to get them going. Obviously the wiring will have to be done, so you may need an electrician for that.
Some of them, in particular the Aeotec brand from Aeon Labs, are on the official “works with SmartThings” compatibility list, which means you don’t need custom code for them. However, if you want to use many of the advanced features, then you may have to go to community – created custom code anyway just to get that. And to be honest, the parameter settings on all of these devices are pretty complex, but there will always be community members who will be glad to help you figure out exactly what you need.
Using custom code in smartthings is pretty straightforward. Basically you copy the author’s code and then paste it into your own account. Once that happens, there will be setup wizards inside the SmartThings mobile app from the custom code that will help you set or use the features you want.
Here’s the FAQ for using custom code with SmartThings. Hopefully it will demystify the process for you and then you can decide whether you might be open to doing that or not.
Again, if a particular device is on the official list, you won’t need custom code to use it with smart things, but you might still want it to get access to a particular feature.
https://www.smartthings.com/works-with-smartthings/-/filter/brands/aeon-labs