jeez, you just asked everything that is wrong with the default mount and blade behaviour altough because of the incredible race/civ/party/nation/ButNotUlric balance in the game these tend to escape. But i too was baffled by such smart AI who still can not swap from 1Hshield to 2H protoss berserk. So to answer those:
No. No. No aaaaand No.
Detailed answer: Ai will not swap 1h to lance, lance to 2h or 2h to shield + anything smart. Actually, you're lucky is Ai spawns with both choices, 1H sheld AND!! 2h separately. AI will spawn with lance plus one of those choices, but in any given situation AI will not choose a smart solution to combat and will stand on the horse poking hopelessly with a 300 range lance. Or 300 of your bow-rider-knights will take 20 minutes to finish their last halberdier, dancing around him firing neverending haikus. + Give them three or eight quivers of arrows they will still use only one. Supported by fellow pendorists and recently just tested it,
if the ai doesn't have melee then the AI will PUNCH empty handed, riding
spirit horses at slow pace, no matter if their other option is a noldor bow and 300 arrows at 450 prof, 300 warp and chain lightning with expert air magic. 3 weapons is not too much for the Ai to handle because AI will actually equip only 2; use only 1 but better not be a crossbow on a horse like the vulnerable maiden or a honor lance on your eventide tanks
For gameplay purposes, the AI will still equip randomly any option you give them. so if you give your knights 1h, shield, 2h, lance.. chances are some will spawn with 2h and shield and lance, some with 1h and shield and 2h, some with 2h and a shield on the back, with a lance as second. I find myself oftenly fighting along the
bloody french sarleon simply because they are so vulnerable, but with a few upgrades their knights become pure swadia armaggedon, with their limited 1h-2h options. If you give the AI a ranged option, the AI will equip a melee option and a ranged option with only one quiver of arrows. Give them knives and war darts, they will only equip one or the other. So, i optimistically conclude with.. NO. there is unfortunately no actual optimal behavior of weapons switching and such heretic activities, but rather think of your CKO as completely moron devoted honorable baby bouncers or something. If you engage them with long lances and heavy horses and stick them against huskarls, you will lose them. If you two-hand-them against noldor, on a 100-hp-fast-horse who gets killed in one shot and leaves them standing with no shield same fate..But rune-axe-them against Anaconda and Cobra and stand and laugh while your 300 spartans eat more snake than Bear Grylls in episode 5. Fortunately everything in Pendor has balance and compensates for what the original engine somehow lacks. Except the Fierdsvain. Fk those unbalanced swine.