Surgie--correct, you can transfer points freely between Marriott Rewards and Starwood Preferred Guest (1 SPG point is worth 3 Marriott Rewards no matter which way you're transferring). And, they do have status match. So, if you're Silver/Gold/Platinum with Marriott, you can link your account and automatically get the corresponding status at Starwood properties. BUT, you don't get night credits, both in terms of staying 3 nights at the Swan/Dolphin cannot be transferred to 3 night credits with Marriott, AND, with the status match, you can't then start adding nights in the other.
In other words, if I've got 70 nights at Marriott, I'm gold, and get reciprocal status at Starwood. But, if I then stay 5 nights at the Swan, those nights don't transfer, and make me platinum at Marriott, with a corresponding upgrade at Starwood. I would still be gold with Marriott, with 70 nights, and the gold equivalency with Starwood, with 5 nights.
Also, this is a bit quirky, but the status match doesn't appear to update. In other words, if you are gold with Marriott, and link your accounts, you get the same status at Starwood. If you then achieve platinum, your Starwood won't automatically update. You'll have to go back through linking (it only takes a minute or two, but it is easy to overlook).