IMHO R&P is an improvement over TMWWBK, being the next iteration.
That said, you can run TMWBK without any changes, since it includes different rifle types. Lesser rifle for the Prussians, better rifle for the French.
I don't recall longer range guns but then you don't need artillery for skirmishes, eh?
R&P does have shock cavalry. Perhaps rate the Prussians as shock infantry, since those have a shorter range than standard infantry.
And perhaps rate regular French as Sharpshooters, since their Chassepots are so superior.
Gardes Mobiles and such can be green infantry, no sharpshooter rating since they have the lesser Tabatier rifles, still out-ranging the Dreyse Needle gun. Hmm, sounds like no rules changes needed if you rate the troops correctly. Same as above for artillery.
Might have to run some skirmishes myself, since we have 15mm FPW figures aplenty.