izigame.me

I had this DLC installed the whole time I played Outer Wilds, since I bought the two together as a Steam bundle. I knew from the DLC description above where its content started ("A new museum exhibit that marks the trailhead for one last journey into the wilds"), and I chose to avoid engaging with it until I'd completed the base game. I think approaching the DLC like this worked well for me. Having completed everything now, I think I might have found the DLC content a bit... distracting?... if I'd started to investigate it while still trying to work out all that was going on with the base game. Also, I found the DLC's revelations more impactful because I had a good understanding of the solar system's history, i.e. things that I uncovered in the base game.
That said, the game devs have done things in such a way that you can in theory engage with the DLC's content at any point, and it will all still work. Deferring the DLC's content worked well for me, but someone who dug deep into the DLC earlier in the base game would still have a perfectly valid (although different) experience. I said it was more impactful for me because of my understanding of the solar system's history, but perhaps if you learn the DLC's story first, it will simply change which discoveries will cause the lightbulb moments for you.
When you first start up the game with the DLC installed, it brings up a warning saying something along the lines of "some players find the DLC too scary, there's a 'reduced frights' option in the settings menu if you need it." So, that foreshadows a tonal shift from the base game, and indeed, I did find the DLC had quite a different tone and a slightly different rhythm to the core Outer Wilds game.
I first started following the breadcrumbs from the new museum exhibit almost immediately after completing the base game, and initially wasn't that enamoured, probably because of that tone change. However, coming back to it after a few days, I was ready to approach it on its own terms, and found it just as awe-inspiring and clever and engaging as the original game. While the content is fairly self-contained (a necessary requirement for an optional add-on) and initially appears to be largely unrelated to the base game, completing the DLC will give you a greater understanding of the overall story of the base game and answers questions you may not have even realised you had.
The DLC is perhaps a bit more linear than base Outer Wilds, as there are some fairly significant discoveries which act as gateways to further progress, and thus if you miss or misinterpret them you can find yourself in a position where you believe that you've explored everything you can and seem to be at an impasse. This is just speculation on my part though, I didn't experience this myself.
There are some sections of the DLC which I've seen some players complain about in comments. The assumption seems to be that because the DLC has mechanics to support a particular approach, that approach must be the expected way to solve things. This assumption isn't always valid however - there is often more than one solution/approach that works, and if you get stuck on this perhaps there's a better way. The base game had a few similar situations, where if you get the wrong end of the stick you might decide that the way to solve something seems to be very hard to pull off, requiring a great deal of manual dexterity or whatever. While it might be possible to do it that way, it might also be a sign that you're not seeing a better way to do it.
Overall, I highly recommend Echoes of the Eye to anyone who enjoyed Outer Wilds.