Just to be noted those are my personal take on things and the correctness of it is up to debate. Just that lot of sources have slightly varying information.
I have been wondering about the Mihara smiths too, as it is very rare to encounter one that would have been attributed to late Kamakura by authorities. Of course dealers will tout Ko-Mihara attributed blades as late Kamakura items, and I admit for many mumei swords I have personally late Kamakura - Nanbokuchō as the range. The different generations might be bit varying from book to book. For example for Ko-Mihara Masaie there are 7 different one in Nihontō Meikan and 5 in Sesko Index. For Ko-Mihara Masahiro there are 3 different ones in Nihontō Meikan and 2 in Seskos. Here the notable difference is that Meikan has 1st Masahiro working roughly 1320s to 1330s while in Seskos the first gen is listed c 1360's. There are actually few items that are attributed to late Kamakura Mihara Masahiro by authorities.
However all dated items I have found by Ko-Mihara smiths so far are from Nanbokuchō to Ōei. Range is 1353 to 1415 among 15 dated blades.
Then you have Kokubunji Sukekuni at late Kamakura, for him there are few dated blades ranging 1323 to 1329.
Then for Hokke
Chikatsugu has 1352 dated blade
Kaneyasu has several blades 1369 and 1370
There are 5 other dated Hokke blades by various smiths ranging 1367 to 1390
For Ichijō I have only found 1411 dated blade
And one 1459 dated ōdachi by 2 Hokke smiths
Then there is Tatsubō school in Bingo province
And for them I have 4 dated blades ranging 1365 to 1373
Here is one problem that I am not sure about, I am not sure if the attribution Hokke Ichijō (法華一乗) is referring to one smith/lineage or a larger group among Hokke smiths. And of course attributions are attributions they need to throw out some fitting classification bracket.