16A AC is fine for the majority of applications
My main concern is the lack of tech specs
If you use this relay as a comparison

If you wanted to switch DC eg solar battery bank then that 16A turns to 300mA
Also depending on load type, voltage, frequency, etc the rating can be reduced
To me the Shelly 1 is marketed as only a 110/240V AC resistive load switch
As soon as you start switching DC or inductive loads I think it will fail quite quickly
I’ve had a few remotely switchable plugs fail where the contacts either weld closed or start generating excessive heat and that’s just because of using them for devices that have built in AC motors (inductive load), you can also see that rating in the spec above, 4000VA but only 550W inductive
AC1 - Non-inductive or slightly inductive loads, example: resistive furnaces, heaters
AC15 - Control of A.C. electromagnetic loads
DC1 - Non Inductive or slightly inductive loads, resistance furnaces, heaters