I watch the mempool every day, and I feel that retail investors probably don't need to memorize all the details of "block builders/relays/bundles"; knowing two things is enough: first, the transaction you send may not be included in the block in the order you see; often, they are bundled into a "private channel" and sent away, so outsiders can't see it; second, the purpose of this is usually to reduce front-running or sandwich attacks, at the cost of sacrificing some "visibility."

Recently, someone complained again that validators are getting too full and MEV ordering is unfair... Frankly, it's always been unfair, you just couldn't see it before. My approach is very simple: large or easily front-run operations try to go through RPCs or aggregators that have MEV protection; small transactions can be casual—don't risk using them as teaching material just to save a little gas. Just remember: public broadcasting = easy to monitor; private submission = less risk of being attacked, but don't blindly trust it.