I don’t understand if I can use illustrations from undraw website (there is information that everyone can use illustrations everywhere for free - “All images, assets and vectors published on unDraw can be used for free. You can use them for noncommercial and commercial purposes. You do not need to ask permission from or provide credit to the creator or unDraw”).
And can I use pictures from unsplash or pexels in my themeforest project?
Yes, you can use it for your projects, although I don’t recommend it for TF.
And use Unplash only if you are a visual designer, I don’t recommend it if you don’t have visual skills.