He was definitely a bruiser rather than a technical fighter. That was very evident when he fought the real Thor, and even Dargo Ktor, another Mjolnir-wielding mortal who was a slicker fighter than Eric was.
That said, Eric was in some ways a smarter fighter than the real Thor, because he was willing to fight dirty, rather than adhere to a code of honour. For example, he wrapped his cape around Ulik's head to blind him, so he could land some cheap shots, which is something the real Thor wouldn't have done.
Also, when he realised that Dargo was a better fighter than he was, he stopped trying to match him in skill, and just smashed the ground hard enough to launch Dargo into the air, allowing him to connect with Dargo while he was in midair.
He later did the same thing against Lady Sif, when he was wielding the Thunderstrike mace.
Heimdall also noted that Eric's skills improved over time.