I would say to stay away from the mainsheet type jammer, cost is higher, more to go wrong and not sure you get the best cleat for the job in them.
I would, and have gone for the cleat on a height block with a fairlead.
I find the fairlead over the cleat lets me as a helm adjust the genoa sheet from an aft angle when the spi is up and it always goes into the cleat. Some people like them open to let you adjust the sheet from an aft or forward position, the choice is yours!
Then have a floating ratchet block which is NOT automatic, a switched one is best so it lets you have it on or off as that clicking in light winds drives me mad!!!! Also a ratchet that has some adjustment in the time or weight it comes on for differing crew strengths.
It is a 35 to 40mm dia block, I find i dont need the 52mm size and this one needs less room for fitting. Fit a hold up spring as a floating block falls over and hits things.
Not that the others do not do a good job but after years of sailing I go for Harken, the cost to me is worth it as they just work and feel so good. But we all have a budget and Harken can take a big lump out of it!!!!
Ratchet and good cleats also allow you to use a thinner sheet that goes through the fairleads and blocks better in light winds.