Some people use game bird feed for the higher protein, if their layer feed is too low and they don't have other options, like an all flock type of feed that's higher in protein. 16% is what the egg industry has determined to be the bare minimum they can get away with and still get eggs in the short term, but they aren't interested in the hens' long term or overall health, since they only use them for 1-2 seasons when they're most productive, then discard them. And since that's the industry standard, a lot of feed brands just go along with that, so it's a common protein percentage in layer feed. It could work for your flock, or it could not - some people see signs of protein deficiency, like feather picking and eating, difficulty or slowness regrowing feathers after molt, etc. 20% protein is a better feed overall, for all ages and all seasons, because it provides enough extra protein to cover heavy protein needs like egg production or feather growth, but it's not so much that it starts becoming a problem (for example the meat bird feeds that are 22-24% protein are too much for regular chickens - they were meant to put on muscle mass fast for fast-growing broilers). So, while you may be fine with 16%, you will definitely be better off with 20%, so in that situation, if I had the choice, I'd choose better safe than sorry and go with 20%.
I make it with cold water in the summer, to help them cool off, and with hot water in the winter, so it's steamy warm by the time I take it out and it can help them warm up from the inside. Not that they really need it - they are wrapped in down coats - but I imagine it must feel nice on a cold morning. This is my way of giving them "treats" without actually giving them treats and compromising their nutrition. It's our hangout time - I sit with them, they eat it out of my hands, then they hang out with me and we have a nice chat about life.
