For UI elements the combo Affinity Photo + Designer might be interesting. As myclay mentioned you can pass data back and forth between vector and pixel graphics pretty seamlessly. Come to think of another thing Affinity is sorely missing but Photoshop has had since time immemorial is animation capabilities (timeline…
When I'm editing anim GIFs, two tools I use regularly are Screen2GIF and GIF Movie Gear. Screen2GIF has really good auto-palette features on save, and GIF Movie Gear is unparalleled on per-frame editing & optimization.