To say that a populist is not like other politicians is therefore to say next to nothing. What matters are the policies.
Is Johnson in favour of keeping Britain in the EU or taking it out? Does he want to let immigration rip and spend more on housing benefits, or cut both? It all depends on who he is talking to, and what they want to hear. Johnson is far closer to the stand-up comedian, who advances his career by tailoring his material to suit his audience, than the leader with a programme for national renewal Britain needs.
I am sure he can act the part as he can act so many other parts. But for how long would he be able to maintain the pretence?