In series you add the Voltage together and in parallel you add the Amps

So a 100W panel with 27Voc will give about 3,7 A and two in series will be 54V and 3,7 A (27V + 27V)

If you are connecting two or more panels of different wattage then the amp will be a bit tricky to calculate, so in series its preferable to have the same specs

In a parellel setup it will be  27V and 7,41 A, (3,7A + 3,7A)

This is just a guidance for you when you are about to buy a solar regulator or add another solar panel

When you are connecting in series measure the voltage with a multimeter to make sure the voltage is below max on your solar regulator.

When linking two or more solar panels together, the voltage can rise to levels that are not only uncomfortable but potentially hazardous, so be careful!