When in Play mode, one has the option of using "Basic Decks" or "Custom Decks", presuming you have constructed one. Does this option match you only with other players that are using the same deck mode? (Likewise, does Casual vs. Ranked have any bearing?)
No, deck choice does not have an impact on who you are paired with in matchmaking (Play mode).
You will, however, be paired with players of similar skill, so at the low levels you may find more people using Basic decks.