Either should be fine. We are using a PAM8306 on our upcoming Bela cape rev C2, for what it's worth.
frfr do we need an extra power supply?
It depends on how you are powering your board. You can try with USB power and getting the 5V from P1.05 and see if it works OK, but if you experience misbehaviours of the board (e.g.: IDE stops working, board shuts down) when driving the speakers close to full power, then you should get an external power supply to power the amp board directly.
When you make connections between BelaMini and the amp, connect the amp's L+, R+ or A+ pin to the L or R pin on Bela's line out (the little 3x1 socket header) and the L-, R- or A- pin of the amp to the ground that's also on that header. If you power the amp from Bela, use P1.05 for 5V and P1.16 GND and do not use the GND from the heapdhone/line-out/analog-in connectors for power.