Making a grilling station: a few Puck.js questions

so you would recommend not to use D28/D29 to make sure I do not enable serial? There are plenty pins available, so I can easily do that.

If you have spare pins then it's easier to avoid them just to be sure. On the MDBT42 breakout the pin numbers are different though (they're labelled as RX and TX and D28/29 are fine to use).

What's the way to tune screen refresh rate? Do I get it right it is 5 sec by default?

Yes - it's 5 seconds. At the moment there isn't any way to do it. You could just copy the module itself into your code and then change it there, or could guess the interval's ID and use changeInterval. Honestly though I don't think it'll make any real difference to power consumption.

I'd be pretty sure the most power is either used when the display is completely static, or when Puck.js wakes up to update the display.