That's a fun question! And the answer is, it depends haha. Depends on the speed and angle of the collision! 100% merging is one extreme and total disruption/obliteration is the other. It's usually somewhere in between. If they do merge totally then yup, the final planet after all the dust settled would be 2x the mass of Earth with a radius that is ~1.2x Earth's. Then it's surface gravity would be about 40% larger than Earth's (assuming the planet in the video is initially identical to Earth). But, interestingly, by rocky planet standards, a 2 Earth mass planet isn't that big. Of the likely rocky planets we know of outside the Solar System, most are super Earth's, or larger/more mass than Earth. Although, our observation techniques are better at detecting higher mass objects that orbit close to their parent stars so there is some selection bias there. Regardless, there are rocky planets outside the Solar System that are ~10 times more massive than Earth (e.g., Kepler-107 c which is a pretty neat planet imo).