everything depends on pike and collected location.
Dwarf pikes seems to do great with pebbles and small plants, maybe a cave. Most are sexed by spots on the dorsal and some the females get red/orange belly.
Bigger pikes def want wood or some cover with rocks or sand. watch your filters with sand when they make a pit it gets messy. Sexing can be done by color changes, white stripe on dorsal and tail for females or the red/orange belly.
For an age, depends on growth. some can tell by about a yr...