If one thing is for sure, you can definitely differentiate someone's musical instrument playing style. That definitely wasn't an imposter playing those basslines post-67. That unique style comes from the inside. Only Paul could have done that. Maybe Paul started plastic surgery early because he didn't want to look like the chubby pug that he was... and then the band joked around about it saying "Paul is dead" because he looked different. In fact, it was the band that started the hoax.