I haven't used Moen, but have had a lead detection shut-off in a previous house (unknown brand, might have been Moen, who knows? it was a rental) and have a current leak detection system so I have some experience with them.

The leak detectors are generally under sinks and pipes. Placement is important, because often there are drips as people who just washed their hands move their wet hands to where the towel is. You need your leak detector out of this path.

In humid weather, condensation will often form on cold water pipes. That condensation can drip onto the leak detector. Sometimes a lot of dust can cause a problem, too, if you have a leak detector in a back corner of the basement or back corner of an under-sink cabinet.

Because one drop of condensation from a pipe can set off your leak detector, you don't want any system with an automatic water shut-off that does not inform you of what leak detector triggered the shut-off. There is nothing more tedious than having the water not turn on and having to inspect all your leak detectors, trying to figure out which one set it off and how to fix it so your water comes on. Particularly if you discover the problem when you go to turn on your shower in the morning or right before you start cooking dinner, etc, etc.

I'd advise a system that beeps or otherwise informs you of a leak, not an automatic shut-off.

I've installed a couple of Moen Flo valves in new construction where the owners' insurance company required them. It is installed on the incoming main water supply to the home. The Moen Flo doesn't have leak sensors, it's a "smart valve." It learns your water use patterns and has the ability to shut off the flow when it infers a leak. That's very different from hard-wired leak sensors which sense a leak. If you install one, check with your insurance carrier about a discount on your homeowners' insurance.

Thanks Charles and Sigrid for your help!

If I am to buy and install a "leak detector," which brand/model would you recommend and where should I install it? Thanks again!

The answer depends on the specific leak detection, and the leak abatement method to be installed, if any.

The Moen Flo valve provides whole-house protection, so it's a good solution, in my opinion. If you want detection only, Moen makes inexpensive detectors that report into the Moen app which you can install on your phone. But you'll need to take action when a leak is detected, like turning off water to a specific use point or closing the main shutoff valve to your home. Murphy's Law suggests that leaks will occur when you're not home to take action. I suggest some sort of automated shutoff valve. I have used the Watts A2C-WB for sensing and protecting against washing machine leaks and the Floodmaster RS-094 for protecting against hot water heater leaks in an attic (for the record, I think installing hot water heaters in attics should be illegal.)