People say that quick play affects competitive. Those people are wrong. See Initial Competitive Skill Rating, Decrypted
To answer the OP’s question, when my main placed 1300, I made an alt who placed at 2156. After playing on both accounts for a hundred games, the gold account remained gold, and the sliver account remained silver (Overwatch Forums).
I then switched back to my main, almost full time. It took me a few hundred more games for it to catch up to my alt (in gold).