In his RE verse, what is Thor's fighting style like? What's his default weaponry, would he have a preference for a specific weapon? In a sneaking section, how would he go about it since he doesn't like to sneak?
Thor is the guy who moves toward the danger.
Not because he's reckless, but because he genuinely believes someone has to be the one standing between civilians and whatever nightmare just crawled out of a lab. He's less acrobatic than Leon, less technical than Jill, and less disciplined than Chris.
Instead, he relies on physical strength, endurance, intimidation, and relentless pressure.
Thor's fighting style would be rough, practical, and powerful. He's military trained, he's been a boxer in his spare time and probably did some wrestling in high school. He's the TANK of the team. He'll also fight dirty when he needs to. He likes to get inside an opponent's reach and stay there.
He will use guns, of course he does. Assault rifles are comfort weapons. He loves to use shotguns, but he's a heavy hitter. He will absolutely use two handed weapons that pack a furious punch.
Mjolnir exist in this world but its a massive ridiculous custom anti material rifle. Its enormous and ridiculous that it has its own nickname because when Thor pulls the trigger something is struck by lightning. Barrett M82A1
Stormbreaker is a high powered axe and a prototype type designed for armored mutations and every bit as devastating as you'd think it would be. These are the sorts of weapons that appear when equipment stops working.
When it comes to firearms when he can't be stealthy he'd be quite the lethal sharp shooter from a distance. He'd favor clean shots and precision. He's only chaotic when he's up close. He'd use a HK417 for that. A side arm would include a SIG p226.
In those situations his goal is to minimize catastrophe not presence. He doesn't aim to become invisible. Its mainly just become non hostile enough to get the job done. He's not sneaking as a concept, he's containing himself. That mean that he's moving slower than usual, checking sightlines constantly, choosing cover big enough to hide him ( rare ) , and accepting that silence is a tool. He struggles with stealth only because of his sheer size. It doesn't suit him and if he can avoid it he will.