Lately, I keep hearing people talk about block builders and bundles, and it seems retail investors don't need to force themselves to be "the person who understands everything."

You only need to know one thing: the transaction you submit isn't necessarily included in the block in the order you expect; it might be bundled together with others, or someone might be watching your path and eating up some of the edges.
To put it simply: don’t think that on-chain = completely fair queuing.

Right now, I only do these few steps:
Check the slippage and minimum transaction amount before placing an order, don’t be greedy and set it too tight;
Use private relays/anti-front-running tools if possible (not expecting invincibility, but at least reducing the target on your back);
Test with small amounts first, like yesterday I lost 8 USDT trying out the route, waited over ten seconds for confirmation before adding more.

Recently, the labels on on-chain data tools have been criticized for lagging and misleading, which is normal…
Labels are just “post-hoc explanations,” if you really want to assess risk, look at the transaction behavior itself: path, gas, whether it’s repeatedly canceled and resubmitted.
As for who the builder is or how the bundle is assembled, knowing that “you can’t see the matching happening behind the scenes” is enough; digging deeper can easily lead you into stories.
That’s all for now.