One problem with two wires is the bottom one gets in contact with a lot of grass and weeds with no room for a cow to stick her head underneath to graze.

Assuming your perimeter fences are good, for interior dividers I would put up one wire at 32" on good, more/closer pigtail step in posts with a real hot 6 joule charger and good grounding system. Small calves may occasionally get underneath but generally won't stray too far from mama on the other side. Calves will either get back on their own or mama will let you know to help.

Young calves will sometimes just go right through 2 wires also, so I'd focus on putting up one good hot wire with pigtails close enough and wire taut enough to maintain 32" height. That is also why I like aluminum wire rather than poly for these long interior dividers. Aluminum can be pulled tighter  with less stretch than poly.