The cells has been shown to improved user techniques, that can apply to obito's katon as well.
-improved izanagi time
Eh no.uchiha's can perform izanagi on cost of sharingan but adding both senju dna makes it complete or to make it reach its full potential since its basically application of COAT [
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danzo's was unable to control hashirama's cells thus his izanagi was incomplete [
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-improved koto cooldown time
yes becoz of the stamina granted to him by hashirama's cells.we have already seen obito using kamui multiple times unlike sasuke and itachi who ms techs drained them after few usage
- improved edo tensei bind
maybe becoz it allows to suppress chakra.It has already shown ability to suppress bijuu and jinchuriki chakra so yeah it will obviously help the edo tensei binding
- improved mangekyou by decreasing blindness limit (not confirmed but likely)
maybe becoz it gives user hashirama's healing factor.we have seen danzo using shishui's mangekyo for more than a decade without any blindness or backlash
- improved chakra levels (which goes hand in hand with stronger jutsus)
we know it increases stamina but that doesn't mean your jutsu gets a boost