No, an increase in pressure reading may be detected, but that is not indicative of a better lubrication, because when the engine is started, it is cold, and a more viscous oil (higher SAE number), will be harder to pump, reason why it will reach the farther zones of the engine, which translates into more wear and tare.
No, it is the contrary. The previous answer is what led the international automotives manufacturers to recommend multigrade lubricants, such as Repsol Elaion (15W-40, 10W-30 and 5W-40) or Diesel type Repsol Extra Life Plus(15W-40), which at the time of the boot-start, the most critical of the operation, quickly reaches higher areas on the engine, thus beginning to decrease wear and tare in this part. Then, when in full regime, they are much more viscous than a SAE 40, although such a change is not detected by normal gauges.
All lubricants were developed thinking of the possibility to be mixed with other lubricants of all other known brand, regardless of the API quality level.