Trekkers Only! : what episodes of Enterprise relate to the other series?

I heard there was a Carbon Creek episode that was good bc it relates to first contact and there's another one that also relates to the aftermath of the first contact movie. is there anything else that you can watch if you're not a big fan of the series but maybe want to see things that are important to other series and stuff.

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There's a mirror universe episode where we find out what happened to the Defiant that went missing in TOS. There's also an arc where we discover the story behind the discrepancy between TOS and TNG/movie Klingon foreheads.
oh and the final episode has Riker.

"He's dusted, busted and disgusted, but he's ok"

"Observer Effect" where the Orgainians come aboard, possessing several crew members. There's the episode where the Ferengi try to rob the ship, and
the Borg episode were fragments from "First Contact" re-animate. The story ends with the Borg sending a message to the Delta Quadrant that would reach it's destination about the time of TNG.

I just saw the Borg episode. It's almost comic the way people were underestimating the Borg.

I think like Star Trek Voyager this show struggled a bit with tone. It seemed like a very serious dark episode and the full darkness of the Borg coming is treated rather light-heartedly in that episode.

I also wonder how the captain was so dumb as to even think he had a chance at rescuing those people