Dave if anything Pochettino is far more rigorous than Koeman - he absolutely flushed out the club anyone who didn't get 100% on board with him - including some players that had been highly touted, paid big money for etc, this season with both Janssen and Sissoko he has shown he doesn't care about what was paid, if you don't produce the form he wants then you are out the teams fast
Spurs and Pochettino if they buy him won't spend 1-2 seasons trying to round out his flaws in his game, they are expecting a title challenge and to do well in the CL - they won't have time to let Barkley learn on the job. Absolute career suicide for the lad if he ends up at Spurs - he hasn't got the right mentality to play in that side.
Best bet for him is Arsenal - he will get a manager who indulges players and effectively lets them slack hugely in Wenger, but he will get to show up now and again and look the player he could have been.
No satisfaction in this at all btw, but if the lad thinks the grass is greener then good luck to him, and strangely he will be one ex player i have no fear of playing up against as i can guarantee he wont show up in those games