Yes, a lot of the brake vans were NEX (
https://www.ltsv.com/rd/tops_detail.php?id=T-NEX), so 100mph dual-braked, probably similar for the buffet cars. Later NFX so 110mph I think also.
I used Manchester Piccadilly 1973-1980, at the start of the period the cross-country services were almost all VB Mark 1 (and the 87s weren't built anyway) but towards the end of the period there were some air braked workings which sometimes had 87s.
My regular favourite was the 16:23 Manchester-Coventry which went over to Mark 2 air-braked during the period and was extended to Paddington; it started out as corridor Mark 1 VB with a Class 86 on 5 coaches so had quite sprightly acceleration anyway.
But once the 87s came along the locomotive workings needed careful planning given that a locomotive on an inbound working went to the engine siding and came back on top of a completely different set, and so the 87s needed particular attention to avoid trying to couple them to a VB set.