I like the fox rampage comp helmet with a chin guard.
https://www.jensonusa.com/Fox-Rampage-Comp-Helmet
I've gone over the handlebars 5 times in 5 years as the front tire whipped to the side on gravel, tree debris, speed bumps or pavement separators. I always hit my chin, never the top of my head. The last time November 2017 at 25 mph, I broke my chin. I tried to find a helmet with chin guard weeks before that accident; search engines gave me motorcycle helmets. jensonusa gave me "javascript error" and wouldn't show me this one, which they stock. So I had my jaw wired shut for 7 weeks.
This Rampage has plenty of vents, and riding now in June, I'm not sweating enough to drip into my eyes. Most of my sweat is on top of my head, not under my arms. I only go 8 mph without electricity, 3.5 hours at a time.
The visor looks stupid, but keeps the sun out of my eyes in late evening. I tried without, then put it back on. Probably designed for tree branches in the eye, as it is a "downhill mountain bike racing helmet".
BTW I regularly get over 30 mph down a 15% grade; electricity has nothing to do with it. I was pedal powered down this grade when I hit in November.