Should I connect 4 solar panels (3.6v 900/1A) in parallel, in series or independently to the PCB to gain better power outcome?
just one and the rest kept in the dark.

In this case, you need to wire them in separately.
The next problem is how to combine them. Normally you'd do this with diodes, but at low voltage the overall loss could be high; use Schottky diodes or MOSFETs in &quot;ideal diode&quot; configuration.