Did Insight have a ballistic entry? If so, does NASA plan a ballistic or skip-glide entry for manned missions to Mars?
InSight's landing on Mars was ballistic, see image below:
Currently NASA has no plans to send humans to Mars besides vague notions of 2030s or 2040s however when NASA was working on the constellation program (that was subsequently cancelled) there were plans for Human to Mars missions. In 2009 the "Mars Design Reference Mission 5.0" was created. This architecture probably would have used a "Triconic Aeroshell" as the decent vehicle.
This entry vehicle would have preformed 'aerocapture' to reduce it's speed from interplanetary to orbital by dipping into the atmosphere and burning away it's speed and then once captured, descend further. You could probably consider this a "skip-glide" as it relies on aerodynamics to lift itself back out of the atmosphere.
For more reading on this planned architecture, here is the PDF I got the images from.
As for other manned missions to Mars, SpaceX has previously released a simulation showing what its entry EDL profile would look like and it's not completely ballistic but it's not a skip-glide path either as the spacecraft has a more aerodynamic shape.