Easy to be overwhelmed with the choices. Almost all of the dashcams we discuss here on DCT are only the better/best ones. Lesser cams are neither reliable nor useful. Street Guardian is an Australian company and their cams are designed for those hotter climates. The old original Mobius is also renowned for good reliability in higher heats, but it's outdated sensor isn't good in low light.
I'm a couple hours north of you on I-85 near Greenville, and we get about the same sun and heat in the summer as Atlanta. In my cam testing one thing I do is run them hard in my old workvan doing full-time recording at the highest resoultions and bitrates, which is often closed and in the full sun all day at work. I've had a few cams which gave problems, only on the worst days with most and with ones using LiPo batteries instead of supercaps. Occasionally some will shift focus slightly when parked in the heat but it returns as soon as the cam cools a little. A remote cam can have the main processor stashed out of the sun in a cool location, which is what we need. Not enough choices of them yet
Mounting location also p[lays a role here. Most of today's cars have a 'frit' around the windshield or mirror- the black dotted area. If you can get the cam body behind that it helps with cooling. Until last year when I got my windshield replaced all I had was clear glass- not even a tint band- the worst of the worst. When I tested my K2S, the main unit was tucked over the sun visor, and only on a few of the hottest days did it freeze and stop recording until I restarted it. I haven't had the chance to really 'push' my newest cams in the heat yet; TBH I'm expecting some issues with the 4K models as those push the processor hard. Reducing the resolution will help with that, but then you lose the high-res benefit, so more a 'work-around' than a fix. Most heat-related cam failures are when parking mode is being used; few or the better cams have issues while driving but many cheaper one give trouble then too
I had very good results with my B1W which was the earliest production. They've since changed some things with the cam but I doubt it has affected reliability in heat. It's a small sleek cam which looks like factory equipment. It might be worth looking into. The original Mobius is a match-box sized cam and can be very discreet if mounted well; nothing is better in the heat. I feel safe in recommending the B2W 'rideshare' cam in heat for driving; it's marginal in high-heat parking. And so far the B2K seems to do well with heat; I'm sure it will be OK when driving. Of cams I haven't tried, anything Street Guardian seem to be great for driving recording in heat, as is the Viofo A119V3. The DDPAI Mola seems to do OK as do a few older cams which do 1080/30.
I've noted people having heat-related problems with many popular lower-cost cams like Rexing, Aukey, Crosstour, some mid-grade cams like Garmin, Transcend, and VAVA, and as well as with high priced cams like Blackvue and Thinkware. Heat is tough on cams, but you do have some good to great choices among the bad ones
Phil