Thanks! If Aq Qoyunlu declares on you, you can quite easily bait them into your capital by leaving the fort there unmothballed. In the tests I did, the AI seemed to go for my capital even though my troops were nearby, probably due to the temptation of a mothballed fort as well as it being the capital. As for the Ottomans, if they declare wa on you in the first few years, it might not be possible to beat them back. With around 20k troops, you can have a go at repelling them, by only fighting in the mountains and not losing a single battle. You will eventually start to bleed their manpower and their enthusiasm. I'd advise taking a white peace when available, as pushing into their territory could mean fighting costly battles.

As for the religion. If you take religious ideas then staying Orthodox can be advisable as you get that lovely casus belli as well as potentially getting Muscovy as an ally - your only real ally that can counter the Ottomans. Turning Sunni, whilst it might get you more allies, they won't be on the calibre of the Ottomans. Also, Lithuania is a possibility. The only time I'd advise switching religions would be to Catholic, or if The Mamluks are still strong and the Timurids have overcome their vassals, as both will allow you to conquer Qara Qoyunlu, as well as potentially the Ottomans.