Cherry MX and Topre or Topre clones are completely different switches.
What are you wanting to use the keyboard for primarily? Most people who play FPS games and the like prefer MX Reds so they can tap quickly if needed. Gateron Browns are smoother than Cherry MX Brown IMO and feel better. It would be a good compromise for typing and gaming and would be my personal recommendation for you to start.
If you're interested in trying Topre I would say forget about the Plum and get your hands on a real Topre board like an HHKB or Realforce. They are very different in feel from Cherry MX switches. In layman's terms, Topre feels more "pillowy" and Cherry MX switches are more "snappy" in feel.
Keyboard and switch feel is really very subjective and it's hard to recommend one switch or keyboard type over the other. It's Apples and Oranges really.
Your best bet is to try them out and if it isn't your style, sell it and try another. I know that sounds like an odd recommendation but really nothing can replicate real world use of a keyboard over time instead of relying on something like a switch tester or typing on a keyboard for a few hours.
Oh and one last thing the Realforce TKL RGB that you're talking about I very much doubt it will be compatible with your Cherry MX keycaps unless you buy sliders since Topre boards use proprietary stems.
Google Topre MX sliders and go from there.