Hi,
Jackson's vary, as noted by other responders, but most I've dealt with have needed a great deal of room, shelter (dense plantings) and a quiet environment. The tree setup you mention is ideal, they often adjust well to that, and will show themselves - in general not at al an animal to handle, however.
Croc skinks fascinating but usually shy and retiring, largely nocturnal and need cool temps, in contract to most lizards.
Frilled lizards need lots of space, especially height, high tempos, hi UVB - please see my article on
Frilled Dragons for details,
Enjoy!