One of the most resource intensive functions in a chart is the If statement. In a lot of scenarios, what you can do is leverage the combination of Pick and Match to replicate the functionality while increasing performance.

Example:

=If([Inventory Type]='Individual', Sum(Qty), If([Inventory Type] = 'Bulk', Sum(BulkQty))
Pick(Match([Inventory Type],'Individual','Bulk'),
    Sum(Qty),
    Sum(BulkQty))

If you need an Else condition, there is a neat little trick you can do by adding a ‘+1’ and making the first option the Else result:

Pick(Match([Inventory Type],'Individual','Bulk')+1,
    'Non-Physical Item',
    Sum(Qty),
    Sum(BulkQty))