I'd search for a dedicated chip for the task.
That said, you really don't want to parallel LEDs. Only the cheap ass Chinese designs do that. Every diode is a little different, and you will get current hogging if you parallel them.
I would avoid the buck-boost. Pick a scheme and live with it. My preference would be a discontinuous conduction boost. Keep it simple. A LED can deal with ripple fine since the eye will average out anything over a few hundred Hertz.
If you put enough LEDs in series so that you always need a boost converter, the design becomes very easy with off the shelf chips. What is normally done to make a LED driver is to send the boost inductor output (via blocking diode) to the string of LEDs, and then put a resistor from the LED string to ground. Then set up the voltage sense pin of the boost chip so that it senses the voltage across this resistor. By regulating the voltage across the resistor, you have effectively regulated the current in the LED string. The inductor flies back to whatever voltage is appropriate.
I recall Micrel made some cheap chip to do this, and LTC made a better though more expensive one. If for some reason the diode string is broken, the inductor voltage will fly high enough to damage the driver transistor. Some chips protect for this, and some don't.
But any basic boost converter circuit can be made to do this. The longer the string of LEDs, the less you have to worry about the loss of power in the sense resistor.