Don't want to micro? Try balanced two handed sabres (there are two kinds, get the thin bladed ones - they're more expensive, but clearly superior). Also give them 2x steel bolts + siege Xbows. They won't try to fire the Xbows on the horses, but during sieges, they will use them quite well. Since they don't have shields, you'll want them to be firing during sieges... but on the field those huge sabres have great speed, range, and damage whether on the ground or horseback - and you don't need to worry about the AI thrusting ineffectively or getting stuck up close with a polearm. You also barely need any shield skill or very much agility, so you're free to pump power strike + ironskins... still, it's worth getting 12 agility for 4 riding, a bit of weaponmaster, perhaps some athletics.
Other good options are shield + morningstar, Great Bardiche (the 116 2h type), two handed sarranid maces, swords of war, 2h military cleavers, long arming swords, and even the spiked staff + shield.
I highly recommend against long lances. You can probably get by with light lances or double sided lances, but you said you don't like micromanaging - and you need to micromanage these to get the most from them. I also highly recommend against horse archery of any kind and throwing weapons - these options cost a lot of skill points and have very little value to them... you'd rather have your companions riding around thrashing in melee. I've also had pretty great results using companions as specialized ground archers. They are particularly good with masterwork siege crossbows as when they get up to the higher proficiencies, they'll launch bolts straight through weaker shields. There's obviously something to be said for a companion with 300 archery and 10 powerdraw. They can rack up an unreal amount of kills rather fast. Generally my rule for ground-companions is balanced military pick and heavy board shield + xbow OR bow + 2x arrows + great long bardiche.
