I don't think that this the relative non-restrictive clause, but why is there the comma before
Hobby drones appear in all shapes and sizes, which sometimes makes the process of finding the right drone for your needs difficult.
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The relative clause is not restrictive, but it is not a "non-restrictive relative" in the sense that term is ordinarily used. The comma (or in speech the comma intonation) marks the clause as a supplement to the main clause: the antecedent of which is not any nominal within the clause but the main clause itself. You could paraphrase:
Hobby drones appear in all shapes and sizes; that fact sometimes makes the process of finding the right drone for your needs difficult.