This is good to know as I was considering upgrading.
i had the exact same issues as you’ve described with Mojave. It was 2 months of constant torturous reporting and repetition between myself and apple support. In the end this reduced my battery capacity because Apple support didn’t know how to fix it even though they told me they were aware of it and treated me as though I didn’t know my own laptop. They told me I couldn’t downgrade.
So, I went to the Apple store Genius Bar and got it downgraded to high Sierra again and it was instantly back to normal. They never addressed this issue with Mojave even though Hundreds of thousands of people had the same issue. It seems they’ve just ignored it with this update and carried on.
I’ve a very well looked after 2015 MacBook Pro Retina, and Mojave + incompetence of some Apple crew nearly destroyed it. It also affected brand new 2018 MacBooks at the time last year, so it’s their software but won’t admit it unfortunately.
you’ll find your MacBook doesn’t actually go to sleep, as my logs indicated it was waking up and connecting to WiFi every 10mins and sending data. It also randomly activated FileVault which I never had activated in first place. If it’s the same issue as I had, you’ll need to shut down your MacBook if you’re thinking of putting it to sleep. The fan stops when the lid is down so hence it gets pretty toasty!!