I'm with you on "not ruining it", these cars are already pretty perfect.
For suspension, I'm personally salivating over Ford performance coilovers that we don't get over here (I think they come with one of the special Mk8 editions too). They're KW v3s that were redone according to Ford specs for linear springs, see discussion in
https://www.fiestastoc.com/threads/coilover-suspension-kit-s.322245/. That being said, I think stock suspension for Mk7 is one of the best street options for the car and I'm guessing Mk8 is in the same situation. Either way, don't lower it if possible; it's already as low as it needs to be from the factory (at least Mk7 but I'm guessing Mk8 especially), see discussion here
https://www.fiestastforum.com/threads/feisty-the-family-car.30825/page-4#post-502700
For everything else, I would get whatever is Mountune's equivalent of MP215 kit for Mk7. Its a nice "Stock+" that doesn't change the car's character and keeps the warranty. They also offer a short shifter but I never neded up getting that because my transmission is already notchy and I worry about making it worse.
I'd leave all of the bushings as they are. I heard poly ones feel nice at first but they age less gracefully than rubber ones and they add to NVH.
I would stay away from aftermarket exhausts, especially since Mk8 is already nice and burbly.
In conclusion, don't know what Mk8 edition you have but if you insist on modding it, I would look at some of the "special editions" that came with nicer parts and try to build towards that.