If you have a laptop with a modern Core i5 or i7 and a decent SSD harddisk and 8 GB ram you can do sensible development on it without problems.
But!... You can bring a server with 32 of the fastest xeon cpu's and 256 GB ram to its knees with calculations if you don't know what you're doing. Never mind a laptop.
Depending on Data we could have 40,000 rows with 20-30 columns of figures.
If you're talking about source data then that's peanuts (i.e. no problem). If you're talking about a pivot/straight table chart then you're talking serious performance problems no matter how fast your hardware is. A table box should be able to handle that alright since it doesn't contain expressions, but don't try this in a chart and expect your users to be happy about its performance.
Yes. I was referring to the source data tables. We are using Qlik as reporting tool for 3 legacy systems with 10+ years of data as well as the new system too. Lots of tables imported, leading to large QVW files.