Sonoff Basic switch after.
DO NOT program your switch plugged into the AC. You will let the magic smoke out.
Most USB TTL serial dongles provide the power needed to program the switch with the new software (Tasmota for example). Not all do though.
Once the device has been installed in your home you can use OTA (over the air) updates to upgrade your software. If the switch loses it’s mind and really needs to use the USB programmer, Then disconnect it from the AC, connect the programmer and program. Make sure to disconnect the programmer before connecting the switch to the AC.