It's too early for me to determine what I want. I am still reading.
From reading so far, I am thinking about running in triode mode mainly because plate resistance of triode is much lower than panthode or UL. This will have a big advantage of lowering the output impedance which increase the damping factor of the amp. I am even thinking of using two pairs of output tubes to further lowering the output resistance to increase damping factor.
As for power, I don't think it's that important for me to get over 40W, so power is not important.
I think crossover distortion ( I think it's the same for SS and tube, is when one half turns off and the the other half take on the whole load) get less as output impedance goes lower. that's the reason high end SS amp uses many pair of output transistors to make very high damping factor possible.
Also, I think the theory is the same for SS and tube, even running in class AB, run at high bias so one can get a big class A region. the amp actually work in class A in the first few watts. This is how I design my SS amp, the first 5W is in pure class A to avoid the "U" shape distortion performance. Literally put the crossover point in much higher signal level where a little of the crossover distortion is not important anymore.
Well, this is my theory at the moment. I might change my mind when I learn more. I still yet to learn how to calculate output power in tube PP amps. So I have no idea how much I can get.
thanks