If I am going with the query as mentioned in #3 then it would create an incon...

If I am going with the query as mentioned in #3 then it would create an inconsistency in the code.

I am using block plugin manager to load the commerce_cart block. And I am happy with that approach. I can't find any reason to change the approach, and use a query like this #3.

Considering that the approach for refreshing cart content will not be changed, so, in future I will have to split RefreshPageElementsHelper class into two. One will refresh the status message, and the other will refresh the cart.