What you want is very possible with the right css knowledge. But yes changing the looks of Quasar component’s can sometimes be quite difficult.
You can use other vue components in Quasar app’s with little to no problem. Just do not expect to implement complete UI libraries like Vuetify (without css conflicts).
Using a standard non vue/quasar input will make things a bit more difficult I guess but here’s a simple demo how you can create a vue component from just an input:
https://stackoverflow.com/questions/50857231/vue-js-extend-standard-input-control-e-g-textarea