Hi Victor,
There have already been a couple of posts that might be relevant to your question:
- Different statistics results between sentinel hub statistical API to numpy and rasterstats results
- Retrieving the sentinel L1C 20m grid - #2 by batic
It is quite a complex question to answer, naturally the pixel grid must be modified if the data is outputted in EPSG:4326 (WGS84) because the native projection of the data is in the local UTM zone.
If you still have some questions surrounding this topic, then please let us know!