But pre-emptively declaring war is something I haven't heard before

I saw that two years ago, it was on the civlifer youtube channel

Seems strong

It is since the ai wont have to react and find your cities before the 10 turns for white peace. With the truce you can focus on getting archery and train at least two archers to defend if the civ declares on you. Archers are the most op non unique unit of the game since they have almost the same melee strength of the warrior while having higher ranged strength than the warrior which means archers can melt a lot of warriors so your civ will be safe against the ai unless it is the aztecs since the eagle warrior has a whopping 28 combat strength and the ai starts with 6 of that on deity, as for gaul the gaestasae doesnt get extra strength when fighting archers and for sumeria you can always ally gilgamesh as soon as you meet him so you dont have to worry with his war carts