What you need on cav is reach and damage with your weapon. So, it's: Lancer > 2H > 1H.
That's not to say 1H cav is crap though, you'll kill plenty of infantry and cavalry, just know your limits. if you placed 2 people with the same skill level 1 on a lancer/2h cav and one on a 1h cav - the 1H cav should be losing, you can block their hits and get in close / trick them / time your hits better but they have the upper hand and you should lose your horse in that fight. So avoid fights 1 vrs 1 with lancers unless they're idiots.
Grab a level 0-2 shield if you're any of the above and it's fine for absorbing as many arrows as you'd bother doing with a higher shield most of the time. Generally as a 1H cav, you're out ranged by everyone so you'll be relying more on brute force with armoured horses or manoeuvre and speed to sneak behind people / whip in and out to get hits.
If you go armoured cav you're able to take some knocks in combat / smash people over and survive the ranged barrage (ranged target your horse less too generally - they'll still take pot shots at you though). If you go high maneuver you'll be able to avoid lancers who are generally on faster less maneuverable horses and weave into combat that infantry weren't expecting. If you go high speed, you'll rack up higher damage (to the enemy and yourself if you get hit back) and zoom into and out of combat like a fighter jet before anyone knows what happened.
Whereas lancer cav will rush into the fight, you might benefit from holding back a little until everyone is distracted and engaged - Chaos and the enemies lack of spacial awareness are your friend. Polearms on foot will try to act clueless knowing you're an easy kill, then turn around and rear your horse... Don't fall for it. 2h heros hanging around their spawn acting helpless or AFK are to be avoided too (you shouldn't be back there whoring for AFK kills anyway). Lancers / horse archers will chase you relentlessly. And every ranged on the field will sling a missile at your horse.
As a good 1H cav, you'll need surprise, timing and will need to be able to make split second choices on the right path to take. You should be a team player willing to charge in and help outnumbered infantry by knocking the enemy over and slashing at their backs - Don't try and be a kill whore. Harass and execute their ranged, cause confusion and break up and lure out their groups of troops once they're engaged so your infantry can mop up. You'll piss your money into the wind on upkeep. But it's pretty damned fun and you can wreck some serious havoc!
A loomed weapon and high str / PS are important because you often will only get 1 / 2 passes on a person. Once someone knows you're there, unless they're useless, they can avoid you hitting them or outright down your horse with ease. Once you're dehorsed, you're dead. Simple as that as you're delayed on the spot laying down, it's enough time for a killing blow to your head and a kick slash if you actually survive that.
You'll want a better / bigger shield if you decide to go heavy armoured cav because with slower manoeuvre / speed you'll be taking more ranged to the face as you're an easier target - Not to mention the horse archers running rings around you. If you go the fast horse route (courser) you'll need looms, there's no point being "fast" when someone else is faster via looms and will trail behind your low manoeuvre horse slashing at your heels.
I generally prefer high manoeuvre (arabian / steppe) as you don't even need it loomed to perform. You'll run rings around heavier horses and can change direction on speed demons last minute and watch them stab at air with their spears as they go hurtling past. It's pretty easy to safely dodge and weave around with 5+ other cav chasing you when you're on an arabian warhorse with impunity. Infantry generally do not expect you to make the sort of sudden turns in and out of combat that you're capable of, making you less predictable and thus capable of getting hits in on them even when they're aware you're lurking. Your nemesis is ranged though...
Personally I find throwing weapons marry well with 1H cav and make up for some of the 1H downsides (So long as you don't have super armour, it's bad enough with accuracy). Lancers / xbow cav / horse archers chasing you for their "easy hits" will turn 180 and run like a bitch when you pull out a javelin. Likewise, the 2H / polearm hero lol stabbing at you with impunity isn't so pleased when you chuck shit at their face. You can take out horses if you get close enough and the occasional speed boost javelin toss to the head kill is brutal - Generally though, it's just a good deterrent as a pose to a primary / active weapon.
On
any cav though, do not be "that guy" who knocks over 10 team mates to kill steal. You may not even need to engage to help a team mate, the very act of you being there behind an enemy is enough of a distraction to put them off and cause their death.
