Event fabric is as good as it gets wrt breathability but, since I sweat in just a cotton t-shirt, no "plastic" fabric is going to keep me sweat-free on a long and/or hilly ride.
My Montane Event "Stormrider" is the best of my 4 attempts to locate the Mythical one.
Montane Featherlite - reports on here suggest a very variable jacket. Some are waterproof for hours whilst some, mine, are simply not, and are worse than useless.
Altura Nevis - Good value but a bit bulky and sweaty. I always felt very cold in it.
Endura Gridlock - 100% waterproof and warm but very bulky. Seemed to breath very well.
Montane Event - Light, very breathable, totally waterproof, well thought out features (great wide, velcro, cuffs for gloves, 4 pockets that are also mesh vents) but pricey.
As Charlotte says, you will get wet. My Montane is warmest when wet. When used with a Merino base layer I sometimes don't notice that I'm drenched.