I think the clumping is most common in gels, and usually after your hair has grown a certain length. Gel is pretty good for TWAs, but most naturals I know use it less and less as their hair grew.
The type of leave-in doesn't matter to me, but it does depend on the ingredients or whether or not your hair is wet or dry. Since we're talking wash-n-gos, I can say that Shea Moisture doesn't work well for me at all on wet hair. Water-based leave-ins work better with my styler.
My life is incomplete without a leave-in.
I can't style without it - I needs the conditioner in my life for my hair to act right. Currently I use Kinky-Curly Knot Today for definition more so than as a conditioner, and then mix in a little Giovanni Direct Leave-In, and top it off with my Eco Styler.