If you're looking into playing 1h/Shield cavalry than I suggest 21/15 as below. Five riding is the best amount for if you want to be good on horseback without sacrificing survivability and damage while on foot. I prefer the Destrier to the Barded Warhorse but that's just personal preference. I use a lot of bump slashing along with a lot of regular swings and stabs--I almost never use overheads from horseback; stabs are still good though. As far as weapon reach I have used everything from weapons like the Steel Pick all the way to the Paramerion and had success with all of them. You just need to change up your play style depending on the length of your weapon. If you use something like the Steel Pick or the Iron War Axe then you almost exclusively have to bump slash; no worries, bump slashing isn't difficult. Right now I use a Langes Messer and the length is fine for both styles.
Level 30 (4 420 577 xp)
Strength: 21
Agility: 15
Hit points: 60
Skills to attributes: 2
Ironflesh: 2
Power Strike: 7
Shield: 5
Athletics: 5
Riding: 5
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 5
One Handed: 148
Two Handed: 1
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1