On the video I see the spinner when some forms are opened, but I don’t know what’s show.
Throwing hardware at an app with performance problems rarely helps, but it could help in certain geographical areas with slow connection with UK.
You can try installing the open source server on your own machine and see if there is any improvement. If there is no improvement, this will rule out your options 1, 2 and 3. Doing this test shouldn’t take too long (but I’ve never tried).
If you don’t see any improvement, you will need to go a little deeper and figure out what’s the bottle neck and address that.