The only upgrade in ”quality” of the materials would be In interior touch surfaces, Dash, console, seats etc. higher end cars get better quality interior materials.
Mechanically, electronically, everything is Hyundai on a Genesis, Same parts essentially that you find on other Hyundai models, same part numbers, same manufacturer stamp.
Similar to VW/Audi, Toyota/Lexus, Nissan/Infinity, Dodge/Chrysler/Fiat/Maserati Ford/Lincoln, GM (Chevy/Buick/caddy). Etc.
all the mechanical and electrical parts are the same, most are third party manufactured to the specs of the parent company and shared across all models that use similar parts (things like windows switches and regulators, intake systems, suspension systems, HVAC systems, etc). Essentially everything comes from the same parts bin
obviously different models will have unique parts to that model, but again they are all essentially part ”made by” the parent company.
I will note that Lexus does have a lot of parts that are specific to Lexus and stamped and such, but they also have a lot of parts that are stamped Toyota. Most of the other manufacturers do not make that distinction, I can tell you I have done work on a 2017 Lamborghini and all the parts were marked Audi..
My 2018 Genesis, so far every part I have seen is stamped Hyundai, not sure if that is changing for the newer 2020-2021 models or not, but I doubt it. Even many Kia parts are marked Hyundai.