Fogging is caused by humidity building up on one side of the lens (usually the side closer to your face), which is caused by poor ventilation and you pumping humid air (breathing) into your eye pro.
Mesh has solved this issue by completely removing the glass in favour of a stamped steel foil or a metal grate, the drawbacks though are quite dangerous: repeated impacts on the stamped steel will deform and eventually break the stamped ones, and BBs can shatter when hitting the "grate" and you'll have fragments in your eyes, which kinda defeats the point of having something to protect your eyes.
Glass (polycarbonate) lenses need constant airflow between them and your skin to avoid fogging, try to find the goggles that provide the most ventilation possible either by large ventilation ports or by forcing humid air to escape by using a fan. Yes, they're expensive, but a bit of DIY and a visit to a hardware store can make you save some money.
I've been using some shooting glasses for the last year or so and they are just perfect, the lenses are large giving me a lot of protection yet they rarely fog (had them fogging up on me once, but the weather was humid af and even mesh would have fogged if it could) when I'm not using any kind of mouth protection..
If you want a full seal eye pro I'd suggest to either go for goggles with a fan or something like the Bollé X800..
Thermal (dual pane) lenses work great, but still you need to keep them vented to work, otherwise you'll end up with condensation dripping down the inner lens, though it's nowhere as annoying as proper fog.
Just my 2 cents.
I'll buy a pair of airsoft thermal goggles and test them (valken sierra, found them at 30$ on eBay)