Steph mentions in a video that output tube heaters with DC is guaranteed to be quiet. If that's the case are the hum pots really necessary? Thinking less is more in the signal path.
You still need that 50ohms of resistance on each leg of the heater, you can't just connect the DC directly to the heaters. If you wanted to use a pair of very precision resistors, that is an option.
Yes, trim pots are necessary to eliminate hum well. I modified the original construction by adding Rod Coleman regulators and eliminating the trim pots. Absolute silence and, as a first impression, a clearer sound. This is a good project and worth building.
You still need that 50ohms of resistance on each leg of the heater, you can't just connect the DC directly to the heaters. If you wanted to use a pair of very precision resistors, that is an option.