This is a common misconception, the angle or spray pattern of the nozzle does not influence the pressure leaving the gun. The exception to that would be with 15 and below angles, which doesn't apply to car washing anyway. The only reason why you would go below 40 degrees would be to narrow the spray coverage for when cleaning wheels, in which case a 25-degree is perfectly fine.
What does affect pressure is the orifice size of the nozzle, and this MUST be paired to each specific pressure washer. If you run an orifice too small, you risk overworking the pump and motor, which can lead to tripping the breaker and even total failure of the machine. Going too big wont cause damage, but then you also reduce some of the effectiveness. I get the feeling a lot of people upgrading their gun setup don't take orifice sizing into account.
Most low cost pressure washers from Karcher, Ryobi, Greenworks, Sun Joe are best used with a 2.5 or 3.0 sized nozzle orifice to boost flow rate and deliver 900 - 1000 psi. For the bigger machines like Kranzle, AR and Active, you are opening up to 4.0 - 7.0 orifice to dial down peak pressure.