We had a situation earlier this year when it took a documenmt too long to open up on QV server. After long investigation, it turned out to be a large number of sheets that caused the problem. The document had more than 30 sheets, almost all were with "conditional show" with complex conditions.
After simplifying conditions, open time was cut in half. But the best effect was after removing most of the sheets. Eventually we left only 5 or 6 sheets, and the problem was resolved.
There were no any problems with the other aspects of performance, nor any RAM issues in this situation.