I'm going to buy a Topre board. I like Greens and Clears a lot. Should I go 55g or 45g?
I'm thinking Realforce rather than HHKB because the layout of the HHKB doesn't do anything for me/isn't useful enough to be worth moving to it.
What are the big differences between 45 and 55?
Looks like SpAmRaY has provided some information, so I'll just briefly note that MX reds and browns are 45g, so is 45g Topre, but the 45g Topre feels a little stiffer due to the different force curve (more resistance at the start of the downward stroke).
Having said that, they are nothing like blacks or greens, so I would say 55g Topre would be the one for you.
Also HHKB is only available in 45g - if you did get one of those you would have to modify it to 55g, which would require a donor RealForce or similar.