Recently, I saw someone talking about block builders and bundles, going on about it in a mystical way.

To be honest, retail investors really don't need to memorize every step; I think knowing three things is enough:
Your sent transactions are not necessarily packaged in the order you want;
Some "bundle together" strategies can make your slippage and execution price very random;
And also, don't be too superstitious about the labels of on-chain data tools, recently there have been complaints that label systems are lagging or even misleading, so use them as a reference, not as a verdict.

What I care more about is controllability: split large amounts into batches, tighten slippage, use private transactions/protected routing if possible, anyway, it's okay to be a bit slower, just reduce the chances of being front-run or sniped.
In terms of security, it really is the top priority.
What about you?