ng-repeat is slow, you will know when you have good amount of data to start researching about better performance of ng-repeat.
You first question
if I change $scope.actions in controller to some other value, would it
be updated in ng-repeat?
Yes, however if it doesn't work use angular's '$timeout'
$timeout(function(){
$scope.actions = [];
},0)
Your second question
Is this the best way to update data values for ng-repeat between view
and controller?
it is the best way though it is suggested supplementing ng-repeat with
limitTo together with Infinite scrolling.
Take a look at this stack overflow question