Guess I'm back. ._.

On the topic of multiple seed types, this was possible even before patch 2.3. If you've ever tried planting Prickly Pineapple with anything outside the Glazenut path, you typically got multiple seeds. I remember trying to get Azeyma Rose seeds with Pineapple + Almond and getting like 4 different seeds, though one of them was Azeyma Rose. Prickly Pineapple was a (terrible) wildcard.

Chocobo feed seem to be different, where every combination will yield at least 2 seed types. If that is the case, our goal is to find the combinations that have the highest average yield of the seed we're looking for. For example, it seems like there are already multiple posts on Krakka + Mirror Apple = Curiel reporting painfully low yields. We can rule out that combination as a viable option and opt instead for the already confirmed Krakka + Chamomile, which seems to be roughly 50%.

Anyways, currently testing and have planted

Curiel + Almond
Curiel + Sylkis
Sylkis + Almond
Sylkis + Mandrake
Thavnairian Onion + Krakka
Thavnairian Onion + Sylkis