I had a 20 year relationship with the keys, 10 of which were full time residence.
I also guided out of Hawks Cay Resort on Duck Key (mm 61) for about 6 years.
I left the keys 10 years ago, and now reside in Vero Beach.
With a kayak you will of coarse be limited to protected areas for the most part.
But regardless, there will be good opportunities around the mangrove shorelines.
Also floating/drifting across shallow grassy bottom areas.
In the keys, live bait rules, so be prepared to buy shrimp. Nothing fancy as for rigs is necessary, or needed.
I would be buying a couple of Cajun thunder floats for drifting over the grass for trout. Otherwise just a hook and a shrimp
tossed up under or near the mangroves will produce. Spinners with 10 to 12# line, with about a 12 to 16" double tied with an easy to tie spider hitch, then a short length of fluro leader attached to that. On the float rig just tie the line to the float and a short fluro leader from float to the hook.
If you go to the reef, you will need chum, and you will also need current for best results. Otherwise you will be bottom fishing. Cut bait like squid cut into strips will work fine as will pcs of shrimp, or a pc of what you just caught. BUT, don't cheat on the chum if you want fish. Yellowtails are easy to catch once you get the hang of it, but you need a good current,
and a steady chum flow. A very small #2 live bait hook on 10# fluro with a small split shot a foot above is all you need drifted back with the current with the bail left open. 1/8 to 1/4 oz jigs work well also.