Ooo, What's this potion do?

[Unoriginal]

I came with an interesting character concept: An alchemist artificer that whenever he uses a spell (Fly for example) he instead drinks a potion (Fluff fun) and "mutates" for lack of a better word and in the case of the fly spell, would grow wings.

My first question is: What would be an interesting way to roleplay certain spells? I plan to make as each time I cast a spell it looks different (The first time he casts fireball it comes from his mouth, the next time his hand turns into a dragon head) get as creative as you like!

Honestly you're probably better off not thinking about that too much beforehand, that way you can improvise on the fly when it happens and state whichever wild, bizarre, untested idea pops into your head for the occasion, without preparation mitigating the weird

Second question: how could I optimize my race and background, possibly feats?

Backgrounds aren't an optimization thing.

For the rest, the question is too wide unless you tell us more about what kind of gameplay or abilities you'd like for this character.

Something to remember, though, is that Alchemist Artificier already goes against optimization.

It's not a bad subclass nor an unfun subclass, mind, just not an optimized one.