As im very confused about the "ground loop" concept, are those what ive drawn in red ground loops? Do they matter? And if they do how they affect to the circuit? It is a voltage controlled oscillator, low currents and max frequency about 20khz.

 

If it is low current and low frequency the earth plane does not come into the calculation

 

Without a schematic, we can't even guess if ground loops could be problematic.

 

Here's the schematic

 

Don't see anything that would be affected much by ground loops.