I am trying to calculate the area of agricultural fields in QGIS. If my vector data is in Default WGS 84 - EPSG:4326 geographic projection, the difference between Planimetric and WGS 84 Area Calculation becomes so large. Here is a screenshot of the comparison of results (WGS 84 & Planimetric Area Calculation in EPSG:4326 and EPSG:32635 - WGS 84 / UTM zone 35N Projected Coordinate System) The difference is much smaller in EPSG:32635 Projected Coordinate System.
You can replicate the result with any vector file. Is it all wrong to calculate the area as planar in EPSG:4236 projection?
area_wgs = WGS 84 Area Calculation
area_pla = None/Planimetric Area Calculation