Can I use Smoke and Mirrors with no targets?

No, you cannot play Smoke and Mirrors if you do not have at least two units at different locations.

According to the card text, Smoke and Mirrors requires you to "Choose a unit you control and another unit you control at a different location." Because this is a requirement to play the card, you must have two such units available to target in order to put the spell on the chain.

As established in RiftJudge FAQ #9739, you cannot play a spell without valid targets just to trigger secondary effects (like drawing a card). The "do as much as you can" rule only applies during resolution; you must meet the targeting requirements at the time of casting to legally play the card.