How to ensure 2D content displays correctly on all devices?

Hi,

I'm really struggling with Lens Studio's "Screen Transform" system. I've read the documentation but it doesn't make a lot of sense to me. I'd like to pin four guidance arrows to the left, right, top, and bottom of the screen, ensuring they never overlap Snapchat UI. I thought I could pin to edge and then adjust the padding but this doesn't always work. 

Namely, pinning to the bottom of the screen seems risky. When I do that, I adjust the "Bottom" padding to -4.00 but this doesn't look great on all device types in Lens Studio (and I'm afraid that there are probably devices in the wild with lower resolutions which will cause even bigger problems).

What units are paddings specified in? What's the best way to go about creating 2D elements at the edges of the display that won't also overlap Snap's UX?

Thank you,

Bart