Veehan/Pari seems more logical since both are elder, and didi turning into devrani is rather strange.
Otoh, Kopal was more sympathetic to Veehan, but even aside from that, Pari may not want the stammering brother and may instead prefer the more suave but younger bro. I wonder whether Bharti is going to ask Srivastav for both his daughters, or just one for Veehan?
My guess is that Bharti may want Pari for Veehan & Kopal for Adi, but Adi & Pari may decide to switch, and elope separately, so that Veehan may be forced to marry Kopal to avoid an embarrassment.
Also, the promo of Pari snatching the keys from Bharti - that's something she'd only need to do if she was the younger bahu i.e. Adi's wife. If she were Veehan's wife, she'd be the default choice. The reason Kopal looked @ her & Bharti stunned was probably that she should normally be the rightful 'head bahu'.