How do Brutus, Cassius, Antony, and Octavius show their characters when they parley before the Battle of Philippi?

BRUTUS Words before blows: is it so, countrymen?
OCTAVIUS Not that we love words better, as you do.
BRUTUS Good words are better than bad strokes, Octavius.
ANTONY In your bad strokes, Brutus, you give good words. Witness the hole you made in Caesar's heart, Crying "Long live, hail Caesar."
CASSIUS Antony,The posture of your blows are yet unknown; But for your words, they rob the Hybla bees, And leave them honeyless.
ANTONY Not stingless too.
BRUTUS O yes, and soundless too, For you have stolen their buzzing, Antony, And very wisely threat before you sting.
Shakespeare obviously could not stage the actual battle of Philippi, which is one of the reasons he brings the four principals together in this brief parley before their assembled armies. Notice how they all keep calling each other by their names. This is to keep the audience informed of the identities of all the four men in armor they see on the stage.
Brutus intentionally calls Antony and Octavius "countrymen" to remind them that they are all Romans and to suggest that it would be better to settle their quarrel peacefully than to kill many Roman soldiers. Brutus is essentially a kind, just, and reasonable man. He opens the parley with the hope that the men can arrive at a nonviolent settlement, although he has no intention of surrendering.
Octavius is a young hothead spoiling for a fight. When he says "Not that we love words better, as you do," he is suggesting at least two things. One is that Brutus is a bookworm who spends all his time reading and philosophizing. The other suggestion is that Brutus is afraid to fight and is trying to talk his way out of doing battle.
Both Brutus and Cassius show in their dialogue that they know they are in the weaker position. Antony was correct in telling Octavius earlier:
Tut, I am in their bosoms, and I know Wherefore they do it. They could be content To visit other places; and come down With fearful bravery, thinking by this face To fasten in our thoughts that they have courage; But 'tis not so.
Cassius is always thinking about his own personal advantage. He flatters Antony outrageously when he says: "Antony, the posture of your blows are yet unknown; but for your words, they rob the Hybla bees, And leave them honeyless," he has a dual purpose. He is intentionally referring to what Brutus just said about "words before blows" and reminding Brutus of how he had warned him against trusting Antony and against permitting Antony to address the Roman mob. Cassius also has doubts about the coming battle. He is trying to win Antony's favor so that his life might be spared in the event Antony and Octavius were victorious. Cassius might even be hinting that he could be persuaded to join the other side and fight against Brutus. His line about "the posture of your blows" might be read as follows: "The posture of your blows are yet unknown; but for your words, they rob the Hybla bees, and leave them honeyless." This emphasis on "your" would show clearly that Cassius is not only flattering Antony but reminding Brutus of how Antony's funeral oration put Brutus's speech to shame. Antony's "not stingless too" might have a question mark after it (it does have a question mark in many editions of the play). Antony is not threatening to "sting" his opponents with a swarm of bees but rather is suggesting that his words (meaning his funeral speech) stung both Brutus and Octavius and continues to sting them.
Brutus loses his temper. He does not like to be criticized. He retorts,
O yes, and soundless too. For you have stolen their buzzing, Antony, And very wisely threat before you sting.
These hot words provoke hot words from Antony, who calls them both "villains." Brutus and Cassius now have no chance of settling this matter peacefully.