Hamura got a power up after the Kaguya fight and awakened the Tenseigan!
The tenseigan granted him additional powers like, A Chakra Mode, Flight, Speed, Unlimited Truth Seeking Orbs, Gravity Manipulation, Chakra Absorption and the wheel reincarnation explosion that can split the moon in half. He also created the Stone golem that fought off full Kurama and reflected his bijuu bombs. On top of him having massive six paths chakra. This boost could’ve been enough to close the gap between Kaguya and himself
Next is Hagoromo The Sage of Six Paths and the Creator of all Things
Hagoromo got two more power ups. He bacame the 10 tails jinchuriki But during his lifetime he also obtained ultra particles from a meteorite, it doubled his chakra reserves, cured his chakra illness and amplified his strength
He also created the Shuigu an indestructible ninja tool that allows the user to draw upon an infinite source of water. This Unlimited Water helped an entire country with no water produce rain fall. It could create rivers and produce flash floods. It also has no determined limit and depends on the power of the user. This water also moves at light speed and can shape whatever the wielder wants like ocean serpents.
Kaguya is overall stronger than Hagoromo/Hamura which is confirmed when Hagoromo states “Mother was more powerful than any other” and Kaguya does have the highest Destructive Capacity in the series with the Expansive Truth Seeking Orbs however…what they lack in feats they make up for in haxes. They are relative to Kaguya at full power. In the past we have them fighting Kaguya for months while finding a way to seal her and a way to undo the infinite tsukuyomi. Kaguya couldn't necessarily beat them either during that time which interprets to them being relative to her already, just that she cannot die due to immortality but they definitely closed the gap between Kaguya and themselves and most likely are equivalent in power to their mother during the primes of their lives