Teach me about resolution

Reading about resolution gives me a few questions, I wonder if anyone with deeper knowledge could help me:

- What exactly is high light resolution and how applicable they are in real life? I heard many people said that Gen2+ has better high light resolution in mixed light environment.

I have both Photonis and L3 tubes, but I feel that I really can't tell the differences in an urban environment?

- What's the highest resolution rating currently? I heard resolution is more a rating than actual spec, like how a Res 72 means it's between 72 and 81. Is there anything higher than 81 currently? How about highest high light res?

I remember seeing a few very high spec tubes on sale in range of FOM 3200+ but all of them having Res 81 with 40+ SNR, could you in theory have a high spec tube that's other way around, like 34 SNR but a very high res like 90+? (I know it's not very meaningful other than photography, but just wondering)