What is displayed in the video is exactly what you described in 1. They're called metaballs if you want to search and learn more about them. You'll just need to experiment with the parameters until you get the effect you are aiming for.
To combine different colors, simply use different colors for the base circle object.
Alternatively you can use liquidfunjs, but you'll probably run into the same issues if you don't learn how it works. Basically, you should be able to do what is shown in the video with the built-in physics as well. colludium.itch.io/liquidfun-for-construct-3
Thank's a lot, Sir for your answer!
I read this guideline and do it!
This is good but doesn't all! (I try if it can be better):
But The main problem, for now, is Combine color!
How can I do this ?! (With effects or any other method except Liquidfun.js, I don't think I want to add liquidfun.js because it is very expensive add-on...)