Outside of Xiucoatl B (and excluding the Domain Invasion only legs), PUP can only reach a maximum of SB+70, since the only SBII pieces the job gets are Niqmaddu Ring (SBII+5) and Moonbow Belt/+1 (SBII+10/SBII+15).
Xiucoatl can indeed help you easily get SB+75. Keep in mind that SBII on Divergence B-path weapons is arguably a little deceptive, since the follow-up attack actually means you're also landing more hits than a non OAx/FUA weapon - so you need more subtle blow just to avoid feeding
more TP in the same number of attack rounds than a weapon without those extra attacks. That being said, perhaps worth considering that PUP's other best DPS H2H choice is Kenkonken (a weapon that also feeds a lot of TP due to Mythic OAx, and gets NO subtle blow from weapon... so take that for what you will).
Still, I see B path Divergence weapons as maybe a better choice for some other non-PUP jobs for low TP feed applications. Ninja is a good example - access to NO other SBII gear, a lowman TP feed strategy works pretty well with the job, and plentiful SB through traits, gear like Kendatsuba set, and Myoshu: Ichi if you really need more SB. So a B path Fudo Masamune has some legitimate applications for NIN.
IMO, what you really want to do if you're interested in a low TP feed PUP setup is to just go with a SB+70 set. You need to make a lot of sacrifices if doing that all from gear, but it's pretty easy if you can get Auspice from a WHM (gives SB+25 with WHM Empy+1 feet). So, just need:
(1) Niqmaddu/Moonbow+1: SBII+20
(2) Auspice: SB+25
(3) Take your pick from the following gear to get the remaining SB+25 needed to hit SB+70 (/DNC also gives SB+10, or /NIN for SB+15).
ItemSet 376366
Worth noting that the Dyna-Bastok Volte set usable by PUP also has Subtle Blow on all 5 pieces, but I always hesitate to include Volte gear in set recommendations due to the significant difficulty to obtain. It's also sorta mediocre DPS-wise versus other options - it's not
bad, with decent Acc and STP... but also not great.
Now, if you're lacking a high end PUP master-only DPS weapon, Xiucoatl B is a solid option that doesn't require making an Empy/Mythic/Aeonic. But you'd really be getting that more for the DPS than for the super niche Subtle Blow. TBH, prob makes more sense to just get your hands on a Karambit. Also notable that Xiucoatl B should be a lower priority than Xiucoatl C for most PUPs. If you care at all about fights with the PET doing damage, Xiucoatl C is utterly fantastic.
And of course, the real best answer if you want a low TP feed job to punch stuff is to just use a damn MNK, not a PUP. A lot easier to hit SB cap thanks to Kendatsuba set, better H2H DPS than PUP, and significantly lower TP feed due to (1) Penance/Chi Blast inhibit TP effect and (2) optimal DPS sets not using a weapon with OAx/FUA.