Works, but know what you are getting into. This board does NOT have AUX in, even though it says it does.
Google "sanwu 7492p amplifier" before you buy. Very easy to setup as a Bluetooth speaker system, once you've connected this to power and speakers, it just works. The board will do a little less than 5 watts on 12 volts. Driving the board with 18 volts will get you significantly more power out, at the expense of using slightly odd batteries and charging equipment.
If you are intending to have this device in an enclosure, you must either connect some push buttons to the board to run the volume control, or make the board accessible to the outside world. The volume controls are not entirely Bluetooth linked, and you need access to the buttons or a parallel button to crank it to 11.
The "auxiliary input jack" is ornamental, doesn't do a thing that I've found. There are some online that say it will work as a microphone for Bluetooth calls, but mine didn't work that way. If you want to put AUX into the amplifier, you'll need to solder to the contact points on the Bluetooth module. There are four of them L+,L-,R+,R-. Google the pinout but they're the four pins with corresponding resistors on the main amp board going straight away from the Bluetooth module.
If your board arrives with the speaker explanations covered, the speaker negative terminals are the two inside contacts, the speaker positive are the outside contacts. The right speaker is the two terminals closest to the power jack, left speaker are the ones further away from the power jack.
The output matching network is setup to drive an 8 ohm load. It will work with 4 ohms, but the 7492p chip datasheet includes very specific changes for the inductors and caps to drive four ohm loads. Making this change will require SMD soldering equipment and expertise. Pricing parts for this in the US very quickly rose to near the price of the amplifier board online for quality inductors and caps.