I like to open up Slicex then drag and drop the vocal samples into that, from there I can chop up the vocals however I see fit, then drag the slices of vocals off of the slicex into the automation area of FL, thus leaving a nice waveform of the vocal which I can see. Then I'll throw that onto a mixer channel and add FX as I see fit.
I've been recently practicing working with 'real' vocals, ones that I record myself by singers or friends that have a good voice and good pitch. They are few and far between but it gives tracks much more personality. Accapellas are a good way of practicing arranging vocals though, and tbh many commercial top tracks use them too. Just be sure to use them in an orginal manner (cut, slice, process etc.), not just slap a vocal track on top of it all. I've fallen into that trap too many times.