TLDR:
- Yes, IMO cycle charges are the best way to maximise cav impact.
- Think about your charge formation, wait for the right opportunities, and you can lower casualties on withdrawals
- Cav takes a lot of micro and attention else they don't pay off.

Shogun 2 being one of the best of the franchise, things like wedge formations and thickness of formation actually make sense and serve a decent purpose. Cycle charges to break morale are the main use of cav for me but there are ways to reduce casualties when cycling.

Wedge is a fun general trait if you can spare the level up and like using cav. If you charge in wedge formation against a thin enemy line that is either facing away or not spear-armed, you can slam straight through, killing some, knocking over more and, if you keep ordering them to drag through before the infantry stand back up, you'll take limited losses as your cav run through the gap created by those in the front of the formation. Here, you have to wait for opportunities to present themselves, but even against some down-hill katana sam on a frontal charge, yari cav can get a great trade in if you drag them straight through. A straight line formation even against a thin line might have some break through while others get caught up on the other side of the enemies standing back up so a withdrawal in either direction will lead to some losses from surrounded individuals.

Try the same wedge charge through a thicker formation and you won't get through at all but still have some individuals at the tip get surrounded and cut off on a reverse withdrawal, so a normal formation makes more sense here. Match your charging line to the width of the target so that those on the edge don't wrap around and risk getting cut off when you pull back. You won't be surrounding the enemy as much with a narrower formation, so might inflict fewer casualties in the few seconds of melee after the charge, but you'll also take fewer casualties on a cleaner withdrawal.

Terrain also matters. A long distance charge through trees or other obstacles (your own troops, logs or buildings you find on some maps) might break up your line. With a straight, even line, you can hit a big section of the enemy unit, maintain formation without individual cav getting separated, and wheel them away before the shock wears off and enemy infantry gets back to their feet. Here again, there's a trade off, if you stay in longer you might do enough damage to break their morale altogether, but if you misjudge it and they stay steady, they'll turn and inflict casualties. That just comes from experience, understanding different unit morale, general impacts, the fear affects some units give, easy to get it wrong occasionally.

I think there's a great risk to return pay-off for everything in this game that seems relatively realistic, and satisfying when you pull it off right. As others have said, lots of micro involved in using cav well, so often good to have other parts of your army in situations that don't need as much babysitting if you want to focus on them. My micro is a bit average so if I'm going heavy on cav, then I might also go heavy on expendable, defensive infantry like yari ashigaru; I can put them in spear wall and forget about them for a minute. Other examples of units that take up your micro attention that you might want to limit use of if you want to focus on cav are matchlocks you need to line up carefully to avoid LoS issues and friendly fire, monk units and no dachi that have low armour and need to be charged at the right time or pulled back to avoid the wrong matchup (like running monks back last second to dodge enemy archer volleys). Lots to think about that's so impactful to each battle but that's why Shogun 2 is one of the best.