is there a difference in results if for example V1a plate is 150v from a 300v B+ into a 220k plate resistor vs 150v at the plate from a 350v B+ into an 330k plate resistor? ...
In Absolute Terms, yes there is a difference.
In Practical Terms, there is nearly no difference for V1 in a guitar amp.
Below are loadlines for the 2 conditions you want: 220kΩ plate load with a 300v supply idling at 150v plate, and 330kΩ with 350v supply idling at 150v plate.
(https://i.imgur.com/ntSxuBY.png)
The 330kΩ with the higher supply voltage accepts a little larger input signal, delivers a little more output signal before severe distortion, and exhibits a little more gain.
- However, rhe output signals realized depend on the input signal applied.
- Input will likely be closer to 100-200 millivolts rather than 1.3+ volts.
- Output for either is 14.8v peak to 15.3v peak, with very little (if any) difference in distortion.
- Gain, output, and input-headroom for both versions will be eroded by the Input Resistance of the next stage.
- The 330kΩ case will have its apparent advantage eroded more by that Input Resistance.
Net Result: they're basically "the same" when looking at the V1 position.