What oranges to use? I only have cuties at home right now.

This looks like a typo in the recipe. The first one is bolded and then there’s another numeral one, which makes it look like 11 eggs. Is that what the recipe calls for?
1 1 large egg plus 3 yolks

Cuties are basically mandarins, so you could definitely use them. Kinda hard to juice them, but be persistent

Since you are marmalading them for the topping ideally one would use fruit that has the thinnest pith (the white part) as possible since that's what is bitter.

You should also look for fruit whose skin hasn't been treated with anything.

For me I usually buy at my town's farmers market or sometimes I'm lucky to be gifted homegrown fruit from neighbors. I won't use store bought fruit for making candied citrus peels.

Best of luck.