Almost all the heirlooms are accessible with the new tab (at least with subscription-like-account on PTR), with exception to
Dread Pirate Ring, which is not listed anywhere in the tab (even after typing a name for the search function to find). Those with DPR, do you also see this?
Another observation with heirlooms from the heirloom tab: one can transmog the non-guild BoAs at 1 gold per item, though if you attempt to transmog a guild boa (helm, cloak, and leggings), the transmog price jumps to 30+ gold (all at level 20). This is not the case though if one attempts to mog a non-BoA helm/leg/cloak with their BoA counterparts (like transmog
Bloody Twilight Cloak to have
Worn Stoneskin Gargoyle Cape mog).