Is faith a universal value on spiritual path and can we mix with strong adepts of other paths?

Yes, faith is a universal truth, it applies to all paths.

There are paths that move along very different lines and mixing them can create confusion. At the same time, certain lines converge, for example Vaishnava bhakti converges in certain ways with Sri Krishna. In general, there are three kinds of paths, very broadly so to say. Those that take us away from the creation as for example the Buddhist approach, those that assure us a dwelling in the Beyond after death such as certain dualist schools, and those that strive to make earth better such as the idea of Rama Rajya, Sri Krishna of the Gita and Sri Aurobindo.

There are common elements in them, and a seeker who knows the goal can pick up helpful elements from different systems such as mind control from the Buddhist system and Raja Yoga. So, a very strict water tight compartment does not exist. Often it can colour bhakti with the ego by thinking my guru is best or the only one and thereby stop progressing. Because it is not so much the human form of the guru but the Divine Presence in him.

One’s seeking may take one beyond the ‘physical guru’ which is not a mixing of faith but a change of the path or a heightening and widening of faith. What is however true is that the surrender has to be to one Guru whom one trusts or has faith in that he will take you to the goal. Assuming of course that the goal is clear because one is conscious of the core aspiration for true spiritual journey begins with that.