61.31(l) says, in pertinent part:
(1) This section does not require a category and class rating for aircraft not type-certificated as airplanes, rotorcraft, gliders, lighter-than-air aircraft, powered-lifts, powered parachutes, or weight-shift-control aircraft.
Since an experimental Xenos is not "type certificated" this exception releases the pilot from the requirement to have an appropriate category/class rating in order to fly it. However, 61.31(l) goes on to say
(2) The rating limitations of this section do not apply to—
(iii) The holder of a pilot certificate when operating an aircraft under the authority of-
(B) An experimental certificate, unless the operation involves carrying a passenger;
So, under this provision of 61.31 the FAA could construe that the pilot would need to hold a "GLIDER" rating in order to carry a passenger in a Xenos if it were certificated as a "GLIDER". However, a pilot flying solo would not, as per the exception found in 61.31(l)(1).
To your other point, flying the Xenos as a glider would not limit you to under 10,000 feet day only. Those are Sport Pilot limitations that are not imposed on a Private Pilot with a GLIDER rating. If the pilot is a SPORT pilot, then yes, he or she would be limited as you describe. That is not an aircraft limitation, but rather a Sport Pilot limitation.
IFR would be allowed so long as the aircraft were properly equipped and the pilot properly rated.
Hope this helps!