The answer is a lot wider than I would like to write.
I have a Ebay cheap PWN, this is a dc-dc converter. I also have a a buck.
Now the difference between the two should be known. a PWN (dc-dc) just turns on and off to change the voltage and the current remains the same. a Buck does the same, however the difference is that there is a inductor (L) and the drop in voltage increases the current (i).
The Load (R) is dependent on the panel and power (W) of the two. if they are not equal then there is a sag on current or voltage. these are rather the same over apposing differences as the sag is inclusive of W.
There is NO point in a boost converter. Any set up using this is pointless unless its for SOS needs. a low power panel Boosting its voltage, with lower the current, typically the lower voltage panel with have a low current in the first instance and therefore you will brown out.
If you use a higher power panel, for example; 255w, Voc38 Vmp33.6 Isc8.8 Imp 8.3
I used a Buck with CC and CV To charge a battery (14.7v).
my current read 7.47, my solar input voltage was 34.4.
Therefore as the voltage was divided the current went up. (38/14.7=2.585)
If my current read 7.47 I divide this by 2.585 and this would give me the current (2.889). Therefore my total power on the solar was... (42.478) as was the power into the battery (-2%).
Solar has voltage but not current, the more sun you get the more current you get.
if you were using a boost converter, then the difference would be taken from the current (ohms law) say we have a 12v panel, and wanted to charge a 24v battery (28.6) the Voc is 17.85 and the panel is 80w. (I is W/V) 2.1917
we will say that its a bit cloudy and and your getting 40% (80-60%=32w) (0.8767 I/2)
and we need to double the voltage. we then get 25v (28v) with a 0.438 current.
Now depending on the type of battery you have, if you have less than 5 amps you can damage a battery trying to charge it. however this could be used for a non use standby battery (if they accept the low (trickle) charge).
You could use Super caps