Greetings, so the inference from the question is DRA is the radiating element of the MIMO configuration. If it is so coupling factor could be inferred from the ECC parameter since the Envelope correlation coefficient (ECC) is used to characterize the coupling performance of mimo for which options are there in CST. For finding loaded and unloaded q factor usage of the conventional formula of q factor I.e.( f0/Bw)could be used and the same could be evaluated from scattering parameter in cST.
if you have any two coupled resonators which do not resonante (e.g. coupled cavities) ) you get a mode splitting i.e. you see two transmission peaks (e.g. the zero mode and the Pi mode) and also two resonances in reflection.For each of the the different Q values can be calculated