Honestly I've always classified "Synths" as any synth sound that is reliant on an envelope, so like stabs, wubs, swells, etc. Even if those sounds could be used as leads, I classify them as synths. The only time I really classify "Leads" is when the sound is sustained, not used as a bass or stab, not used as a pluck, etc. It has to be a legato sound.
That said, I hadn't really made much in the "Lead" department. I don't use legato leads much, I use a lot of stabs. That probably came from my disdain for supersaws being overused. For this pack, I took a different approach with FM & AM Modulation, and the PHS/FLNG Filters. Got some CRAZY sounds that I will be using tf out of. Really really really stoked about this pack.