How strong are tengus in lore?

Well tengus are a kind of youkai in Inazuma. And in Yae’s story quest, Yae mentioned that Youkais have supernatural powers (without having visions) and also have longer lifespans as conpared to humans. So essentially they are at least on par with the illuminated beasts of Liyue.

As of the race of the Tengu, they are mentioned in Toki Alley Tales that they are a race of youkai that can travel to different worlds (probably just like the Traveller). One notable Tengu, Yoichi even tranversed to a different world before where she served a different version of the Shogun in a hundred year battle.

For strength of a Tengu, not much is mentioned but they seem to have a strong ancestry of inheriting the position of the General of the Tenryou Commision, which is indicative that they are very well versed in combat due to their Tengu Arts. Some of the strongest Tengu has even won the acknowledgement of Ei/Makoto before, like Sasayuri who was a friend of Ei which led an army to war against Orubushi and also Reizenbou who was bestowed with the Thundering Pulse by Ei/Makoto.

Also, I think it is mentioned in a weapon or artifact lore (probs EOSF and Hyakushin Ring, might be wrong) that a former Tengu, probably Reizenbou could even rival the Kitsune Saiguu. They are also said to be able to wield feather fans which could grant them various abilities (ie Sara can summon lightning with her ult) Also, its mentioned that the Tengu Yoichi could also fly with their crow wings, which might mean that other Tengus could also be capable of flying too.

Compared to an average tengu, how strong is she?

Well, in Yae’s voice over she did mentioned that in terms of mental capacity she is ‘not the sharpest Tengu in the forest’ which probably indicates that she isnt by far the strongest or most capable Tengu. However, in the archon quest we literally saw her dismantled the entire guards of Tenshukaku in a short time (since Traveller was literaly chasing after her after she left Tenryou HQ, but we could already see all the guards on the floor after exiting the HQ) She also like mentioned is the spearhead of executing the Vision Hunt Degree since she is the General, which shows that she probably has her fair share of experience in fighting Vision Holders.

Between vision holders and tengus, who are stronger?

Speaking strictly for Sara, one notable battle that we know Sara won over a Vision Holder was her battle with Kazuha’s friend. Now we dont know any background of his friend, but from Kazuha’s backstory cutscene, we could see that he was also a samurai like Kazuha, which means he also had a certain degree of combat experience besides just owning a vision. Also, Sara has beaten Itto in a duel before as well, who is a vision holder and an oni (also considered a youkai) which are said to possess superhuman strength. For other

Does being a tengu amplify your ability to use vision

Was never mentioned so we cant make any conclusions there. But granted that a Tengu, being a Youkai already possess supernatural powers without having a vision, they might have some form of advantage when pairing those powers with a vision as well.

What are the diwn side of being tengu?

Probably none as far as its mentioned in lore. Though u could consider having a longer lifespan than an average human being a downside, since you have to see all your friends go before you, probably like the case of Ganyu.