Tube amp question

I am a novice tube amp owner. I have had my Black Ice Audio Fusion F22 for not quite a year. I want to understand plate voltage and how it impacts tubes or vice versa. I want to roll the tubes to the KT150's which Black Ice has said can be used without issue. The plate voltage of the amp is 500v. In other posts, someone said that KT150's require a minimum of 600v at the plate. Since Black Ice says their amp can use them, does this rating depend on the circuit? I have some basic understanding of electronic circuits and I googled plate voltage but I'm still not clear on what it is exactly. Can someone knowledgeable with tube amps help me understand this? Thanks!