Solar fuseing, confuseing

If you have more than 2 panels in parallel you need to fuse each one. This is a code requirement. It's also to prevent a fire. If one of the panels shorts out the others (3 in your case) will try to deliver their Isc thru the shorted panel. This would be more current than it is designed to handle and likely cause a fire. Therefore, I would strongly recommend installing the "string fuses" as they are called in the industry.
However, if your MPPT controller can handle the voltage of all 4 panels in series then I would wire them that way. In that case there is no need for a fuse on the input of the controller. It could never blow.