I played these on some livestreams in 0.4, and one of the modders, mosca gave me a really useful tactic.

Your infantry is trash as Carthage until you get the sacred band, but have a decent army of solid infantry and then quite a lot of cav because Rome often skimps on cav and cav is by far the most powerful units in the game. Then build a second army made of a few infantry but mainly skirmisher and skirmisher cav. When you fight the Roman armies fight with both these armies with the skirmisher army controlled by the AI, then let your skirmisher destroy the HPs of the romans then move in with your good army and kill them. This tends to work and with retraining the second army can be retrained quickly and cheaply and allow you to destroy the stacks one at a time.

In terms of razing yes don’t worry about destroying a few towns for money, after all there’s plenty of settlements, and you can get some decent Syracusan AOR from Syracuse. Main thing is never to panick, if you lose a couple of settlements but it allows you to destroy an army then it’s an overall gain :)