Can I use Google Apps Script instead of Formulas for doing calculations on a spreadsheet?

Question

1. Is Google Apps Script faster than FORMULAS for calculating sum or
   sumif in a spreadsheet which has around 10,000 rows?
2. How does FORMULA work?
3. I know Google Apps Script executes its code in the cloud, but is there any way for that to work client-side just like JavaScript?

Answer 1

1. Is Google Apps Script faster than FORMULAS for calculating sum or sumif in a spreadsheet which has around 10000 rows?

   No

2. How does FORMULA work?

   Client side, can cause desync issues but refreshing the page brings you back to what everyone else sees. So there is actually a server side and client side execution of these formulas to a certain extent

3. I know Google Apps Script executes its code in the cloud, but is there any way for that to work client-side just like JavaScript?

   No