Nettle fibres are between three and six inches long I find, but I know someone who breaks them out so aggressively that hers are as short as cotton....and inch long cotton fibre is a good one.
Nettles were used here to spin fibre finer than flax, and nettle cloth is absolutely beautiful.
Flax fibres come out sort of golden creamy coloured but nettle comes out white. It doesn't need bleached.
Hair is blooming awkward stuff to spin. It honestly depends on the hair. I have long hair, it's shiny and it doesn't stay in a spin. I have a friend whose mum's family come from India and her hair is beautiful, long and very slightly textured, not quite curly, but not straight. It spins beautifully, and it stays in it's ply too.
I wonder if our hair is "too clean" - there aren't enough oils in it to enable it to 'bind' as it's spun; we use too much soap and detergent. Mesolithic man would not have had that problem

Does horse tail spin better than human hair?