Hi, @abruescas and I have explained the noise results of C2RCC for S2 in another thread.
Please have a look hear: How to calculate Chl from Sentinel 2 Level 2A images - #6 by Marco_EOM
Regarding your follow up question: You can export the bands to GeoTIFF if you like, or set pins to certain locations (import your sites) and export these to a text file. Or, you can use the Pixel extraction tool (Raster / Export / Extract Pixel Values).