From what I understand wide short spool like on the JM sig series spinning reel will cast longer, but a narrow one will be retrieve easier with donwside being more memory then wider.

Is this correct?

My problem with the wide arbor spinning reels is that many production rods don't have the proper guide sizing and placement to take full advantage of the spool difference. The IPT retrieved is a function of both spool size and gearing, so I don't think ease of retrieve is a major factor. As for line memory, braid and KVD Line & Lure are ways to address that if necessary.

I was also concerned about the wider spools and too small a first guide, but have not found that to be an issue at all.  I'm using a 40 size large spool reel on a Loomis SJR 783 which has what appears to be a size 25 first guide.  The reel is spooled with braided line and the fact that it is so limp is likely why there haven't been any problems.