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Hello, i only use my Ipad and my app favourites are:

Union App: For easy blends, because i can draw with my pencil so good.
Procreate: This is for Draw, with some brushes that i made for some effects.
Plotagraph: This is your favourite, this is for get animations from the pictures (have a Desktop app too for windows).
Icolorama: With Icolorama sometimes i get some interesting pencil draws that i after retouch.
Reversee: To find the picture i like with the best resolution.
Aliensky: Some camera effects, planets, stars... all in png format.
Glazé app: With this i can transform one picture in a Oil Draw, but there is a trick, use different filters and after blend the sections that you like with one or other oil effect .
FMP: My video editor, easy and effective.
Lightroom: Don´t need words about it.

I wish you can try to get any interesting art with these programs, i only use this and some other, but the more important are this.

Wow, thank you for this comprehensive list! I will definitely have to check these out and see if can figure out some tricks. Thanks again for your awesome answer! Cheers!