If your BCR alrealy control Totalmix parameters, I don't think there's any other option to activate (and on my setup, if I don't tick "Submix Linked to MIDI Control", the submixes are never selected).
BUT, if you simply move an output fader, it will NOT select directly the corresponding submix.
The behavior is not exaclty the same with the mouse : when you move a fader with the mouse, 2 steps are made in the same time : moving the fader AND select the submix.
With a MIDI Controller, you must use a dedicated switch (button) to select each submix, because sometimes you just need to select a submix to see Input and playback faders' view without moving the output level.
I don't know if you use your BCR with MC mode or standard MIDI CC ?
With standard MIDI CC, submixes select CC are
Ch13 / CC 104=>117 and Ch14 / CC102 to CC117 (NB : Ch13 / CC102 is use for Trim Gains)
(or in hexa : BC CC68=>73 and BC CC66=>73, see the manual for more infos)
As far as I remember with the BCF2000 (I never used any BCR), you could program it to send 2 CC in the same time (1 CC to select the submix and 1 CC to send the fader value). Then you could have the same behavior as using the mouse.
(PS : Si tu veux qu'on discute en français, on peut peut-être poursuivre la discussion sur AF ou MacMusic, je poste en anglais ici car ça peut aider d'autres utilisateurs).
RME UFX - TM FX 1.05 / Drivers USB 2.03 fw 1.58
Mac OSX.8.5 / Pro Tools 10.3.10+11.3.1 / VEP 5.3.1