...you can hear the fans working & the metal casing of the laptop becomes very hot. MacBooks are great but I think that is the only let down that when editing on FCP, you can't even have your laptop on your lap as it becomes too hot...
I have 2015, 2016 and 2019 MacBook Pros, and had numerous Windows laptops. All laptops in that same category are like that. Your 2019 MBP 16 is not over-heating and is working normally. In general the 2019 16" is better than earlier ones, but all high performance laptops behave that way.
Apple is attempting to address this by changing to ARM CPUs, aka "Apple Silicon". The first ARM MacBook will be out this year. We can then examine the difference it makes regarding thermals, battery life and fan noise.
A significant improvement should be possible, since the A12Z CPU in the new iPad Pro has about the same GeekBench numbers as the Intel i7-7700K in the top-spec 2017 iMac 27. The iMac fans spin up frequently, whereas the iPad Pro doesn't even have a fan.
My god, I understand you so well, my friend! This is a common problem, because Final Cut is not like playing chess on your laptop, it's a huge soft that is capable of rendering in 8k nowadays. That is the exact reason why it's so hard for it to stay chill ha-ha! Anyway, I know that if you go to a place like
starlabs laptop repair
, you can have your productivity improved and your cooler upgraded. Obviously, it will cost you some money, but I think you are ready to spend a little if you are already owning a MacBook and a final cut pro!
The reason fans run and the case gets hot is precisely because the cooling system is doing its job. This will vary with your media, unrendered GPU-heavy effects, and the processing involved. If you leave it alone for a minute or so, the fans should return to normal. Also, make sure all other apps are closed. It's normal.