Spreadsheet design,which is more efficient: Table + Pivot table or Sheet + Formulas

Hi everyone,

Would you share your experience or best practice in designing a spreadsheet especially when it comes to large spreadsheets.
I found that although using tables to store data and pivot table for reports is cleaner and more organized, the file size get bloated fast even with small amount of data.
However, on other other hand, when I store data on a normal sheet and use formula to create reports is more efficient in terms of file size and speed.
Am I doing something wrong?

I also thinking of putting all the data in Access and just Excel for reporting, but that is extra step.

Any thoughts?

Thank you for looking into this.