With most traffic coming from mobile, ad creatives need to be optimized for smaller screens. Do you design specifically for mobile or repurpose desktop creatives? Have you noticed CTR differences between vertical video ads and standard formats?
Vertical video ads are always more immersive than standard formats. They just fit to the size of a mobile phone screw such that a person that views it doesn't have to stress to view the video. I do vertical video ads and I get very huge impressions from it than standard formats.
You can run ads on reels, stories as well as feed. While designing ads, you need to keep this in mind. Your ad needs to fit to the mobile device, the fest format is always vertical.