@mgamby Welcome to the forum.
The battery life may possibly be improved by installing TLP and cpu frequency indicator. You will not get the battery life you had with Mac os. That was a proprietary os on the manufacturers hardware. Nothing will work like Mac os. As Linux improves we look forward to better battery life, but the companies that have perfected those algorithms for efficiency are not being freely shared, so the devs have to reinvent the wheel if they can't reverse engineer it. Check the tutorials category for installation instructions.
The fans may be due to the wrong or outdated version of the video driver. You may want to search your video card with Ubuntu 20... forgive me, i really dislike and won't use Mac. Maybe a Mac user will jump in here, but this is about as much as i can help. Best of luck.