It has been a long time since I read One Hundred Days but here's what I remember from Admiral Woodward's book.

The most dangerous part of the Argentinean Navy was their naval air force. Their equipment was mostly outdated (they were still trying to drop unguided iron bombs on ships WW2 style!) but their pilots were pretty capable and the AA defenses of the Royal Navy's ships were unsuited for that sort of a threat.

The capabilities of their surface ships weren't impressive. I can't recall if this is from One Hundred Days or from an interview with HMS Conqueror's captain but the RN was very unimpressed by the captain of the General Belgrano. The Belgrano's escorts were completely ineffective and once Conqueror found the ships she had an easy time sinking her. The only real danger they posed would have been if they'd managed to sneak undetected into Exocet range of the RN task force.

Argentina's only functional modern submarine did give the RN a lot of trouble. Here is one source you can read through. TL:DR is that the RN put a lot of effort into hunting the ARA San Luis and it doesn't sound like they ever came close to sinking her. Sonar conditions around the Falklands were tough for sub hunting. Equipment problems may have been part of the reason that the San Luis had no success hitting any RN ships.