Too early to tell on Arsenal, they've had two crappy fixtures with a new manager. They've an easy run now and I expect them to be looking competitive soon enough. I still rate Emery as a manager too. That said, are they vulnerable...sure.
Unless Spurs have some injury issues, they're still solid top 4/5.
Man United...look a mess in this game but who knows. Vulnerable again though. However, they could easily fire Mourinho and get in Pochettino or Zidane perhaps and turn it all around pretty quickly.
Despite all that the door is slightly ajar but it would take us getting sorted defensively speaking pretty quickly.