Well, Hamilton has found Max's pace suspect, but he's always throwing conspiracy theories out there. I don't know why driver opinion matters, we're just talking here. Further, Perez has his job on the line. Of course he's not going to reveal any team secrets. Suspension plays a huge part in aero efficiency, especially under the current rules. If you can control the bottoming of the car, you can stall out the floor and beam wing for things like straight line speed.
Ah good point on that with the suspension and bottoming, I didn't think of that. I believe Lewis called the Red Bull suspicious (which, quite hilariously, he did the weekend after Max's car given the full inspection by the FIA after the race, and passed with flying colours lol).
In regards to the PU's, it makes perfect sense to me that Perez would be getting older, degraded units now. At the start of the season things were equal, but as Perez trashed cars and drove over his head, the team giving him older engines until he straightens out would be the obvious thing to do.
Each car has its pool of engines. The only way for Perez to have a "deficient pool" is for his engines to have tested "less god" than Max's on the dyno before being assigned to a car (when bolted up prior to a race or practice). See comment above. The team CAN give him an ECU that underutilized the engine in his car. But the pool is the engines bolted to his car.