Use inexpensive point sensors in many leak-prone locations. Add an automatic shutoff valve when the cost of an unattended leak justifies the installation and maintenance complexity.
Best simple local alarm: Flood Buzz
Flood Buzz is intentionally simple: place it beneath a sink, appliance, toilet or water heater and it sounds when water bridges its contacts. Current models advertise alarms up to about 95 dB.
This architecture is useful because there is no hub, Wi-Fi or app dependency. The tradeoff is that you must be close enough to hear it.
When automatic shutoff is better
A shutoff product such as Frizzlife LP365 adds a valve that can stop supply water after a sensor detects a leak. That can materially limit damage when nobody is home.
The cost is installation complexity and another powered component in the plumbing system.
Where to place sensors
High-value placements include beneath reverse-osmosis systems, water heaters, washing machines, dishwashers, refrigerators with water lines, toilets and sinks.
Coverage matters more than buying one premium sensor and leaving the rest of the house unmonitored.