Bsd The background is Saba learned from Yisrael Karduner the student of Moshe Breslever who was orphaned and who R' Nathan raised as his own. R' Nachman said only R Nathan knows me. R Nathan had several disciples. So there's no mainstream. Who can say this is chief after this, Rabbeinu ended all that "Dynasty" and institutionalism nipping it in the bud and after and repeatedly battle after battle reaching the highest possible level a mortal can reach in Avodath Hashem until there's no more and he always said No just go in private and talk to God and you all have to do this and just be honest.
Breslev were pretty united as they all know Breslev is just R Nachman until in the last generation b'ah there's some beef between publishers and communities and some "leaders" manhigim start acting Rebbeish and so for example in Saba's recordings and bio Yisrael Sabba he tells how one MSS (mefursam Shel sheker) took all the money which Saba gave all the money he could raise to print Rabbeinu's sefarim non profit and this MMS said he'd help print but instead he built himself a large community and name and acts rebbeish r"l. Probably many members of various communities and mosdot don't hold by these MMS and are NaNaCh to some extent or neutral or ignorant r"l but they might be there bc of the schools, kollel, funds etc.
There's a spectrum of beliefs person to person so to make it brief a few extreme might hold Saba is Mashiach this or that (and since he passed away that would be the only "parallel" to C mashichists, l'habdil NaNaCh would say) or that he is R Nachman in whatever very strict sense they believe. Of course this results in occasionally even some NaNaCh won't accept or welcome each other so I think that will answer your question re other Breslevers, but they would room together for the RH kibbutz in Uman or Yerushalayim, hard to quantify but quantity isn't necessarily definitive anyway so.
Barukh Hashem that we had Sabba here in such recent years who always emphasized Rak Rabbeinu, only Rabbeinu z"l, and not to regard MSS or any other sheker in the world that Rabbeinu warned us against.
As for other orthodox I think the vast don't know what Nanach beliefs are or the relevant essential facts and info imo for example
- What was Rabbeinu's last lesson LM II:8 Tiku - Tokhacha where he finally mentioned the Future Song Y YK YKW YKWK that will be sung with the Moshe Mashiach as in Az Yashir and Rashi and Tikunei Zohar daf 51a-b and where he's saying, Who can be this proper Rebuker who needs this Voice of the Nahar the River from Eden like R Akiba said I'm amazed if anyone now could rebuke the generation etc. of course he's alluding to himself and he himself is rebuking bc why is he dying torturously coughing buckets of blood and the generation did not merit and like Moshe Rabbeinu gave his final rebuke etc etc Na Nach
- What is the Petek the letter that Saba discovered in his locked cabinet that only he had the key to bc the other students at yeshiva R Meir Baal haNess would mess with him r"l
- Videos some viral of people friends of Yoel Ashkenazi who the opposers say was the guy there who forged the Petek just to cheer up Saba from his 17 Tammuz episode and who testify Yoel said God forbid God forbid, Those are lies, I never said I forged it, I did not write that, Saba got that by a miracle ..
For further info I would recommend Yisrael Sabba his recordings or the bio which is the transcript of that, and of course personally talk to H"Y with simplicity and truth and ask which is Hitboddedut which was Rabbeinu's main simple advice. Blessings of Na Nach
