Even if you could type on browns without bottoming out, you'd bottom out on any Topre board due to the force curve. The different Topre switches feel far more like each other than they feel like any other kind of switch, but if I had to compare them to MX switches, I would say that the 45g is a bit like tactile reds (smoother than browns) and the 55g is sort of like non-clicky blues (more tactile than browns). They're both really nice to type on, and I think it mostly depends on whether you want something softer or more poppy.
As far as I know, the "silent" switches don't feel different from the standard ones. Topre switches are already fairly quiet compared to MX ones, and the silencing just makes them quieter on the upstroke.
The 55g model is probably just $50 more expensive since EK's prices seem to change a little based on their current stock. My 55g I bought from them was actually about $50 cheaper than my 45g.
It seems like the 45g model gets a little more love around here, but I think I usually feel more like typing on the 55g one, since I tend to prefer a firmer switch.