that seems... unlikely.
russia would never favor the ottomans after being at war with them for the last 200 years.
Romania-Bulgaria would face some issues initially: 2 language, one in latin and the other the OG Cyrillic. while both are orthodox the romanians still followed the julian calendar so that would also be a problem. finally they would have to decide if the cuntries have some sort of internal indipendence or are united fully. if the latter happens i can see Stambolov become prime minister as he was kinda known in Romania.
the great power won't like it so Romangaria would need a protector, AH most likely since Romania was already CP affiliated. this scenario is more likely after 1885 when Serbia went toward Russia.
the balkans wr will be heavily different. Romangaria won't need help to kick the ottomans. they have basically twice the population of Serbia and Greece combined, a strong german style army ( the pRussia of the balkans, both manpower and equipment available).
in OTL Bulgaria was able to field in the second balkan war 500k soldiers and reached a peak of 1 mln in the WW1. Romangaria might be able to go for 750k soldier without suffering economically if Stambolov was there. 750k that would easily smash the turks, claim MAcedonia and the agean coast. the only reason they would join the balkan alliance is under Russia relation improvement ( economic gifts and stuff) and there won't be a second balkan war unless it escalates to ww1.
one thing i think might happens is romangaria staying pro-cp in ww1, join them but then switch sides like romania in ww2 just to avoid losses and gain transylvania if AH explodes.
Basically, in 1920 there would be a 30/35 mln people country that will care only for it self since they would have achieved everything. ( great romania + great Bulgaria). the only missing thing would be Costantinople which won't be gained unless Turkey/OE ( depends on butterflies) goes fascist. the country might as well change name to third Bulgarian-walacchian empire since it would have almost the same borders it had Bulgaria
with Simeon the Great excluding Serbia and northern greece plus part of hungary
depending on the living standard there might be this
guy parents not emigrating to the US so guess the results...