Research macOS Mojave Feedback
Thanks to a lengthy developer and public macOS Mojave beta, there is a lot of data about how macOS Mojave runs on your type of Mac and how it works with apps and services.
Take some time to look on forums, social media and YouTube for examples of how macOS Mojave works on your specific Mac model and even down to the spec level.
This is recommended for everyone, but practically required if your Mac is one of the oldest that can run Mojave.
You can check the Apple discussion forums for feedback from macOS High Sierra users once this is live and check out the MacRumors forums where you'll find feedback and important app compatibility reports.
At this stage, you won't find many apps that don't work, but if you are reliant on a specific app, check and see if anyone else has any issues running it on macOS 10.14.3.