I wouldn't mix tigs. They are aggressive towards other catfish in particular other Brachyplatystoma. I tried mixing tigs with other tigs, jurus and flavis. I always found one tig would become dominant and start nipping at fins and hoarding food, eventually they would out eat other fish or grow so large the fin nipping was more fatal. The only way I would suggest mixing them is in either a very very large tank, mixing larger more docile fish with smaller tigs. Or similar sized fish in a JDM style tank with lots of dithers.
I love Brachyplatystoma but only a few species make good aquarium residents. My favourites being Juru and Playtnemum. They are both gorgeous (in a different way than tigs), more interesting species, more laid back and not quite as common (platynemum being pretty rare in Canada). Everything else is either impossible to find (vaillanti, capapretum,) too large (filamentosum, rousseauxii,), or super skittish and end up beating themselves up in fish tanks (rousseauxii/flaviscans).
Other similar species have their own challenges too. L.pati needs cooler water so can't be mixed with other species like it and S.planiceps are delicate babies.
It's hard truth about these pims, but unfortunately that's life. They are definitely fish worth keeping if you are willing to meet their requirements, but definitely not something you can just throw in a monster community.
Hope this helps!