For the ATtiny series 1 controllers (e.g. ATTin817) the Touch controller uses the A/D converter (see ATtiny417/817 data sheet, PTC - Peripheral Touch Controller, 32.2 Features: "Using ADC peripheral for signal conversion and acquisition").
The AVR128DA28/32/48/64 data sheet does not mention this limitation. Does that mean that the A/D converter can be used independently while the touch controller is in use? I could not find any explanation of differences in touch functionality and used periphery for different microcontroller families.