The video shows the mixing of two identical guitar recording played through the same amp of Vox AC15. The sound is then curved with different EQ and filtered out with clarity and width with full stereo sound production.
Using one stereo track at a time to make the mix sound fuller and wider is a very good tip. Also avoiding a bunch of stereo tracks is really helpful. In fact picking up one and folding the rest to mono boosts the mix. Working with lesser stereo tracks in a mix like stereo piano, stereo guitar, stereo drum overheads etc helps in creating a better stereo mix.