I’ve got a couple, an Altura Reflex one which is fantastic and a Montane tiny one which is tiny, nonfantastic but still good.
The Altura one’s got a mesh back, which does kinda restrict the waterproofing a bit! But most water hits you in the front especially with a camelbak on. It’s got the react fabric which is highly breathable. This is the only waterproof I’ve ever found that I can wear on a warm day and not feel horrible, it’s a very handy bit of kit.
The Montane one is the size of an apple when packed, and is fully enclosed so good if worn without a camelbak, but a lot more sweaty. It’s showerproof but not waterproof. Useful thing to have as it can just go in my pack and be forgotten about, but it’s not really all that good at what it does. Still, a good compromise, sort of absolute minimum weatherproofing.