In most games, the 3300x stock is slightly higher fps than a 3500x, the core speeds and extra 2 threads helping spread the load around. But considering margins of error, the 2-5fps differences in lows and highs make them basically equitable, especially when paired with a mid-grade gpu like a 2060, where often as not you'll run into gpu restrictions before hitting cpu restrictions.
That makes the 3300x a better value for the buck, IF you can actually get one.
The only time the 2600 becomes the better bargain is if most of the workload is using more than 8 threads, so for production work like rendering etc, it's 12 threads holds the advantage. Otherwise it's @ 10fps avg behind the 3300x/3500x while gaming.