"Real time (not recommended)" is ... well ... not recommended. It is the highest possible priority. Advised in the thread is "Above normal" (i.e. between "High" and "Normal").
On the other hand buffering "Low" is lowest possible setting (i.e. below the advised "Below normal").
I would also suggest to try a different value for Prebuffer (e.g. try 20%) and maybe a bit smaller buffer size.
(Anyway, I suggest to try different percentages and sizes)
