There's no speed or damage penalty for 1H with a shield. Shield weight doesn't even affect the wpf, unlike armor weight. Polearms get a 10% damage malus and a big speed decrease (not sure how much) with a shield on foot.
1½H weapons (bastards, morningstar etc) get a 10% damage malus on foot and 0% on horseback with a big speed decrease.
2H and polearms get a 25% damage malus on horseback afaik as well as a big speed decrease. So for example a Persian Battle Axe deals less damage than a longsword on horseback while having less reach and being far slower.