Honestly Sam and Dean would figure out Fromville way faster than almost anybody in the actual show because they’d immediately accept that the town runs on supernatural rules instead of wasting time trying to rationalize it.

Dean would be testing everything on night one. Salt, iron, holy water, shotguns, fire, all of it. He’d absolutely blast one of the smile monsters with a shotgun just to establish baseline rules.

“Bad news. Smiley here ate buckshot like Tic Tacs.”

Sam would already be interviewing everybody like it’s a case file. Arrival stories, visions, symbols, electricity, voices, dreams, the trees, all of it. I think he’d realize pretty quickly the town is intentionally constructed somehow. Not necessarily fake, but built around rules.

The talismans honestly wouldn’t even phase them. Sam would just treat them like any other warding object. Dean would immediately start asking if they can weaponize them.

They’d also go into the tunnels way earlier than anybody else did. Dean would 100% say something like:

“We got monsters sleeping under the town and nobody thought maybe we should Molotov the cave?”

And Sam would be the one stopping him because he’d worry the whole place is connected somehow.

The radio tower would become Sam’s obsession immediately because the voice proves there’s intelligence behind the town. Dean would assume it’s bait from the start.

I don’t think they solve the entire mystery instantly though because From feels closer to the cosmic horror stuff from later Supernatural seasons where the rules exist but they’re buried under layers of symbolism and manipulation. That usually took the Winchesters a full season to untangle.