Is there any paging build into the PowerApps controls? Lets say you have Gallery control bound to a table with one million rows will it try to load all or should you handle this manually?
The gallery will only load a certain number of items (100 or 500 by default, if I remember correctly), and as the user scrolls towards the end of the gallery, it will load more items from the data source.
Notice that this works only if the expression that is used to define the Items property of the gallery can be run at the server side (delegated). For more information on delegation check out https://learn.microsoft.com/powerapps/maker/canvas-apps/delegation-overview.