You want a rod length that will clear the front bow of your kayak when fighting a fish.
You want a rod length that is manageable inside the kayak.
If vertically storing rods, there are some low bridges where you might have to temporarily hold them in your lap if going under the bridge.

Thus, some of this will be kayak dependent.

For me, somewhere between 6'10 and 7'4" works well.

Lots of personal preference with rod/reel types

If you only want to bring two rods, I'd bring one 7ft medium+ spinning rod and one 7'2 heavy baitcaster.
Some manufacturer's medium is more like a medium+ (Abu Vendetta comes to mind)

I tend to throw small cranks on an Abu Vendetta 7' medium+. Much easier to cast into the wind.
I actually use a Abu Vendetta MH for deep diving cranks--the drag system on spinning reels just works better for crankbaits for me. The MH Vendetta is more like a MH+ --perfect for throwing or trolling bigger crank baits.

Low profile baitcasting reels are smaller/more compact and easier to fit along the the side of a kayak.
Baitcasters work better for me frog fishing, Trig, jigs, crig, pitching.

If you like finesse fishing and you could be talked into bringing 5 rods, I'd go:

6'10 true medium moderate action spinning rod (jerkbaits, very small light cranks, small topwaters)
7' true medium fast action spinning rod (drop shot, light split shot, ned rig, slider head)
7'medium+ fast spinning rod (senkos, flukes, square bills, light shaky head)
7' MH spinning rod fast action(deeper cranks, heavier shaky head, light t rig)
7'2 heavy baitcaster moderate fast action (frogs, pitching/flipping, crig, Trig)