Do the size of the system need to be that much larger for 95C compare to 100C ? In my understanding the post talk about methods that do not involve pressure. On top of that if you want more heat you may simply use a liquid switch higher boiling temp.

Yes because at 100C you can use phase change to transport water, which means you've built a primitive heat pipe.

At 95C H transport is slow so heat will accumulate until it reaches 100. But then you have boiling and, w/out good seals water loss.

We should be able to design the mixer fins and chamber such that it generates some pressure differential between the input and output ports.