Seperate busses and channels

Simple-Does using separate busses for audio and instrument tracks in cubasele8 keep the recorded or live sound from mixing together(interfering) with each other, thereby producing a better sound opposed to having both tracks on the same buss and same channel?
I’m having trouble with good instruments from cubasele8 and good third party instruments when played on two separate tracks but using the same channels and the same busses…so what can I do to get each instrument, say a piano and then a violin keep a “separate” sound or dynamic when played or recorded as piano on instrument track #1 and violin on instrument track#2.Can you show me how to route them separately and still monitor them live? I tried and somehow one instrument will play and not the other…