Do different castes have different Karmic outcomes for the same action?
Yes, different actions produce different karmic fruit for different people, because the Dharma for castes are different.
For example, it is a huge sin for Brahmins to eat onions and garlic, whereas there is no sin for Shudras:
Manu 5.5 - Garlic, leeks and onions, mushrooms and all that proceeds from impure things, are unfit to be eaten by twice-born men.
Manu 5.19 - The mushroom, the village-pig, garlic, the village-cock, onions and leeks,—the twice-born man eating these intentionally would become an outcast.
‘Na pātakam’—‘no sin [for the Shudra], in eating garlic and other forbidden vegetables and fruits’ (Govindarāja and Kullūka),—‘in keeping a slaughter-house’ (Rāghavānanda).
Chapter 3 of the Bhagavad Gita says that it's better to do one's own Dharma than another's:
It is far better to discharge one’s prescribed duties, even though
faultily, than another’s duties perfectly. Destruction in the course
of performing one’s own duty is better than engaging in another’s
duties, for to follow another’s path is dangerous.
Brahmanas who engage in trade practice medicine are to be despised (fallen off from Brahmanhood), whereas trade and business is a required duty for Vaishyas:
8.102 - ‘He shall treat like Śūdras the Brāhmaṇas who tend cattle, who engage in trade, and who are craftsmen, actors, menial servants or money-lenders.’
(Brâhmanas) who neither study nor teach the Veda nor keep sacred fires become equal to Sûdras;
And they quote a verse of Manu on this (subject), 'A twice-born man, who not having studied the Veda applies himself to other (worldly studies), soon falls, even while living, to the condition of a Sûdra, and his descendants after him.'
'(A twice-born man) who does not know the Veda (can)not be (called) a Brâhmana, nor he who lives by trade, nor he who (lives as) an actor, nor he who obeys a Sûdra's commands, nor (he who like) a thief (takes the property of others), nor he who makes his living by the practice of medicine.'
9.326 - After having his sacraments performed, the Vaiśya shall take a wife and apply himself entirely to agriculture and the tending of catlle.
9.328 - The Vaiśya shall never conceive the wish—‘I will not tend cattle;’ and so long as the Vaiśya is willing, they should not be tended by any one else.
9.331 - Also the excellences and defects of commodities, the advantages and disadvantages relating to countries, the profit and loss on merchandise and also cattle-breeding.
Yājñavalkya (Parāśaramādhava-Ācāra, p. 416).—‘Money-lending, agriculture, trade, and cattle-tending have been ordained for the Vaiśya.’
And many more actions such as drinking alcohol, pronouncing the Vedas, etc.
From the Garuda Purana:
The Brāhmiṇ who sells liquors, and consorts with a lowcaste woman; who
kills animals for his own gratification, not for the prescribed
sacrifices of the Vedas;
Who has put aside his Brāhmaṇic duties; who eats flesh and drinks
liquor; who is of unbridled nature; who does not study the Śāstras;
The Śūdra who studies the letter of the Vedas, who drinks the milk of
the tawny cow, who wears the sacred thread or consorts with Brāhmiṇ
Who covets the King's wife; who abducts others' wives, who is lustful
towards virgins, and who slanders virtuous women;--
These, and many other fools, fond of treading forbidden paths, anal abandoning prescribed duties, fall into the Vaitaraṇī [river, which