First, it is not POI alert, it is only target point alert, so only that target ponit can vibrate what you have chosen as guidance.
Refresh rate: press long one of right button for 1 sec, and you can see that the up button icon is a refresh picture. Now press the up button once or more and the refresh rate changed. 1 -> 15 -> 30 -> 60 -> 1 ...
I have Pebble classic, and there is no new firmware for it. But I think, this is a simple app with few feature, so it works with all watch. The new calculated compass function is always accurate when you are moving. (The 12 oclock is the forward direction.)