I believe they are both electronic. I'd be a bit more worried if you had a mechanical low water cut off, there's usually a float in there that may stop working if there's too much sediment. Yours looks like it's just a sensor probe, look up the specs for that cycle guard. The VXT is the auto water feeder. You can easily just test to make sure that they're working, if the boiler is running, you just let enough water out til the low water cut off kicks in and the boiler stops firing. If there's no water in the sight glass and the boiler is still firing, then your low water cut off isn't working. Chances are it probably is working otherwise the boiler would be dead now. But yes, if the low water cut off or the water feeder fails, then it's usually the end of the boiler. Probably why they're only rated for 15-20 years instead of 30-40 years like regular hot water boilers.