Will EMDR help people who are too closed off to use HMR successfully? Or, will they be unable to connect to their problems through EMDR as well?

This is a somewhat complicated picture. On one level, EMDR will appear more successful because such individuals are more likely to have a session with EMDR that tracks something energetically and alleviates it, so it will have the appearance of being a successful achievement. In actuality, the clients will be working only with the most superficial level of the subconscious and the energetic consequences, which are not understood by the individual themselves. So to have a rebalancing and an easing of inner tension is all well and good but it will be quite temporary, so it is a kind of fluffing up that is accomplished and little more. So in a deeper sense and in a practical sense, such individuals are more a challenge than the current psychological tools can truly help with. Such individuals need deep karmic repair with subconscious channeling coupled with trauma resolution to make any headway.