It all depends on the amount of data in a document, the complexity of the expressions used in chart objects, the amount of objects on a sheet and how many apps one user has open simultaneously. A .qvw is often compressed. When loaded in ram it can take up around 7 times the file size. And then the calculation of the expressions and rendering of the sheet objects also uses ram. The simplest way to find out is just open a document, use it and then see what happens with the resource usage. You can get an indicator if you open the sheet properties window and look at the Objects tab, especially the calculation time and memory consumption columns.
And an additional consideration is that when licensing QlikView Desktop using "Borrowed CALs" from a QlikView Server, these can only be applied to two MacAddresses per User. We discourage use of Desktop Virtualisation for QlikView Development due to the resource contention (particularly RAM) caused by concurrent users working on large documents. Publish QlikView Desktop to only two of the Citrix Servers in your Citrix Farm otherwise licensing and activating the software may require individual licences and an exception in your contract with Qlik.
Consumers should use a Browser to interact with the QlikView Server. Resource utilization is centralised on that Server, and the consumers can be on many real or virtual desktops.