What struck me though, referring to Kaffeine, is that once you install Kaffeine AFTER MythtTV, the TV section totally disappears from Kaffeine...
And as far as 'easy' testing is concerned, it would be rather easy to have Kaffeine co-function next to MythTV - Using it from within KDE of course, not from within LinuxMCE.
Kaffeine cannot use the Tuners because MythTV's backend is started on bootup and it takes control of all of the DVB devices that you have configured as capture cards. Once Myth's backend is using the DVB cards no other app can use them until Myth's backend is stopped. This is the ways DVB resources are managed by the system.
All the best