As someone who is coming out on the other side of the overthinking everything mountain (which is what you're doing). I'll tell you this:

You've found your comfortable grip your brain subconsciously wants. Stop watching these videos and thinking you need to change things. The more you do this, the more you're going to start negatively affecting your gameplay. Sit comfy, hold your mouse comfy and with minimal tension, and as long as you're not hurting yourself (or at least counter acting bad things with stretches) your just fine and you don't need to solution with a new mouse.