Harry Veer ji
I begin as follows: It is to clarify that I have never felt any mysticism myself nor have heard any one saying that one has realized the Ultimate.
Meaning of Term
1. a. Immediate consciousness of the transcendent or ultimate reality or God.
b. The experience of such communion as described by mystics.
2. A belief in the existence of realities beyond perceptual or intellectual apprehension that are central to being and directly accessible by subjective experience.
3. Vague, groundless speculation.
http://www.thefreedictionary.com/mysticism
There are two ways of interpreting as to that you are aiming at by mysticism.
1. One way to look at ‘mystical powers’ is to equate these with as super natural powers, spiritual powers, occult powers etc that I would quantify in Punjabi equivalent of
Ridhi,
sidhi etc.
2. The other would be, and more appropriately, the power to commune with the God as and when wished. I make second presumption here that anyone who is in communion of God or is self realized person shall have an access to the powers as stated above @ sl.1 above
Per-Sikhism
There is a reference to
Ridhi,
sidhi etc. in Bani as well. I had searched for ‘supernatural spiritual powers’ and there were about 20 results. You may try out different combination of words at srigranth.org; I am quoting two of these as the meanings of the lines are self contained.
The nine treasures and the miraculous spiritual powers come by contemplating the Immaculate Naam, the Name of the Lord. [220-19]
Those who meditate in remembrance on the True Guru, are blessed with wealth and prosperity, supernatural spiritual powers and the nine treasures.[1405-17]
Your second part of the question relates to whether Gurus had mystical powers. I believe that they were Perfect Human being and self realized persons. Guru Nanak dev ji could turn the direction of the Mosque as per his convenience is an ample proof that Gurus were blessed with the super natural powers, the phenomenon of which we cannot explain.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-sikhi-sikhism/37649-does-sikhism-embrace-mysticism.html