Unfortunately I didn't see the game, did Ajax play with their best fprmation or did they rotate after the tough programme and spare some key players?
I think so too, Ajax have also only conceded 2 goals in the league, sensational. The only rival for me this season is PSV and as you write, the 5:0 was like an execution. But the season is still long.
Of course there are many matches to go, but I believe that playing in the Champions League is no extra burden for Ajax, but rather extra motivation and a way that forces them to keep their game level as high as possible. I don't think PSV can beat Ajax over the course of the season. Ajax has once more a very solid squad.