Glad to see that people are still enjoying this mod, and I'm also so glad that people are enjoying this mod in Cave Story+! Most of the items that you can get in any of the other 3 endings can also be gotten in this path as well. The only main thing is that in the path for the 4th ending, you eventually have to give the blade back to King, and so you don't have the opportunity to trade the blade in for the Nemesis. So, no blade or Nemesis. Also, if you have the missile launcher, then it will not be possible to get the alien medal. You also don't fight the Ma Pignon and get the Mushroom badge. You don't really need that. You also technically don't get the Iron Bond in the path for the 4th ending, but in this case you don't need it to get into the final area.
...This only occurred to me just now as I'm writing this, I don't recall ever testing to see what happens if you pick up Mr. Little in the graveyard and take him with you in the 4th ending. The Mr. Little side quest can't be completed in the 4th ending because you can't access the Outer Wall when going for that path.
Other than that, anything you can get in the other endings you can still get in this ending.