Instagram Ads

Does anyone have experience with insta ads to create an email list i can then retarget to?

Does anyone recommend it?

Yes, you can do that, the same way you can retarget email list via Facebook ads. It's not a bad way of doing it, specialy if you have a warm, big email list.
I would maybe suggest you though to set up a Facebook pixel on your website and use that data to retarget your customers or segment them by ones that took some action.

You can do it, but instagram ads are way more expensive than fb ads

if you want to collect emails then just run lead ads on fb as it will be more cost effective