I saw a description of a linestage using the type 85 tube. It was described as having a cascode 6BL7 output stage. The 85 is a high plate Z, low-ish mu triode. Seems that this output buffer would present a minimal load to its plate.

How to manage the input capacitance? Will a screen grid have more capacitance to grid than the other options? Let me gues...depends on the screen grid...:)
cheers,
Douglas