Why does every fast car at my local autocross look the same?

The crowd is onto somethig real, but probaly not for the reason you think. That combo works becasue it's just physics narrowing things down: low weight, good grip, and stiffness in the right places is what wins tight low-speed courses. When the winning recipe is that obvious, everyone lands on it eventually. It's less copying and more convergence, like how every kitchen ends up with the same three knives.

One thing I'd add from running my own oddball setup for three seasons now: the parts matter way less than people assume untill you're already fast, and the driver skill curve in autocross is steep enough that a year in you're probably leaving seconds on the table that no sway bar will buy back. My suggestion would be to run your current car on good tires for another season, log every course, and compare your sector times against the template cars where they gain on you. If they're beating you in the slaloms it's seat time, if it's the sweepers then maybe the chassis conversation is worth having. Also worth checking which class you'd actually land in, because a copied build can dump you into a stack of national-level drivers.

I chased that same template a few years back on my old coupe. Bought the braces, swapped bars, the whole checklist. Car felt sharper, my times barely moved, and the same guys still beat me by the same margin. What acutally helped was riding along with one of them and having them ride with me. Turns out I was braking way too early everywhere and never knew it.

One thing to check before you buy anything: your local class rules. Some of those bar upgrades can bump you into a tougher class where everyone's got more power than you. That's the trap I fell into, not the parts themselves.

Quick update — I stopped focusing on the parts checklist. Like one person suggested, I spent some time riding with a driver who alredy had the template build. That was the game changer. The technique improvement was way more valuable than any new brace or sway bar.