Ultralinear and Triode. What's the difference

Dennis Had has designed a lot of amps and I've owned a couple of them. The Inspire Firebottle HO (High Output) I currently use (few years now) is designed for Single Ended Class A Pentode use. He's described the design in detail here and there so look around if interested in that, but suffice to say his amps are astonishingly well made point to point wired sonic masterpieces.

From the original posts, sans the heat, I gather:

SETs = 1 triode/channel = low number of high quality watts.

Parallel SET = 2 triodes/channel = more power = some concession on quality?

Pentode and tetrode (P/T) tubes can be wired as triodes, many feel sound better this way.

This not to say P/T tubes wired in triode sound better than a pure triode. However maybe supply more power?

Would love clarification/correction in my gatherings. 

My Muzishare X7 uses KT 88 tubes,  I have a issue with a pop in one spesker when I turn off in ultra linear, but if I turn off in triode it does not pop.

I guess what I'm getting at do those different modes use different parts of the tube?

Could they it be a tube issue?

Amp is brand new