I think the absolute minimum you'd see for the Baltics - and probably Finland - are independent states ruled by German princes, well within the German sphere of interest by inclusion in a German-led economic association and functionally German protectorates, through formal military alliance. The fear of Russian revanche along an extended border with no geographic barriers would be sufficient to ensure that.
Likely as an intermediate possibility is something like the United Baltic Duchy, united more intimately with Germany but still technically independent.
The most that the
Drang Nach Osten crowd could hope for would be three or four new German states, led by German princes, with generous minority and linguistic protections. It's also possible that this could be a later development, with the other possibilities being intermediary steps in that direction, growing closer to Germany through overwhelming economic and military domination, along with some immigration from Germany. Even in this scenario, Balts would have a good deal more freedom and autonomy than they ever had under the Tsars. Finland and Poland still would be independent, however, if still dominated by Germany. Appetites for annexing Polish territory (i.e., the so-called
"Polish Strip") were mixed at best in our own timeline, even late in the war, and would be less in Carlton's timeline here.
A separate but related question for annexation - an old "what if" - is the final destiny of the Austrian Cisleithanian lands*. A successful continental war, especially if only with Russia, would buy some breathing space for Vienna, but only for so long, especially given the growing independence of Hungarian magnates by the early 20th century. The death of Franz Josef would probably hasten that day of reckoning. A successful, fairly liberal (if not "English liberal") dominant Germany would be an attractive union power for the German-dominated half of the old Empire, admitted as one or more federal states under Hapsburg prince(s). But that's a development further down the road, in the late 1910's or 1920's.
(* With some inevitable modifications: Burgenland swapped for Dalmatia and Bosnia, minority protections for Czechs, and Galicia given over to the new Polish state - the latter development eased by a Poland under a Hapsburg or Hapsburg-related prince, if that happens.)