How to compare tires for replacement and needed pressure

I really tired to read all of this but got a headache. I never really cared about speed ratings on my trailer tires. I just scale my trailers and know exactly how much weight my axles are carrying and get the appropriate tires.

In my current FW it was obvious I needed G rated tires instead of the OEM ones they came with. Since I rarely would have the need to exceed 65mph I don't need a chart for any of that.