Every 401k I and my wife have had let us set which index, but would rebalance itself every year because they believe they know better. It’s really annoying, but if you’re familiar with the markets, I would say it’s very necessary. Especially since the default funds will often have fees associated to them.

There are some differences, but real world applications, especially in the gaming space, are minuscule. You do almost touch on another important point; it’s hard to get benchmarks because you’re not going to find a processor that was made for both. Basically a single gen of intel is all we get. FWIW that gen showed a roughly 5% performance on a typical game, and 10% on a known memory intensive game. That’s 3 frames at 60fps, or ~7 frames at 144, and this assumes you actually need that last bit of performance.