Good on Ya all those above on this topic. I agree and appreciate your efforts in getting the right information, a rarity on the internet.
One point to add. Honest (Emission Labs for one) modern tube makers of 45s , 300Bs, and 2A3s freely admit that they cannot hold the bias tolerances nearly as well as RCA, GE, Sylvania, WE and others could in their day. There are lots of reasons for this and I see and agree with what they are up against. Therefore, modern tubes in a cathode bias amp can have quite a range and in some cases run way too cold or way too hot (dissipation wise). Amps with adjustable bias and a way to measure current make these variations unimportant. We use adjustable bias in all our amps except for the EM7-2.5. For those amps we select tubes that fall into a range we like. We make this amp for those who don't want to fool with bias and we take the responsibility of providing selected tubes that hit the right bias point.