I use a grid method. But technically yes, in lines. A buffer does go in circles... but that's buffing. You're using very very fine polish to reduce the appearance of scratches. And, when you do buff, the proper method is also in a grid pattern. Basically left right left right, going down as i go. Then up down up down, going left as i go.
It's not so much the wax itself causing scratches, although it can if it contains light abrasives that are meant to polish on a small level as an all in one product like most OTC waxes. In an ideal environment the wax is pure, contains no fillers or abrasives AND the vehicle surface contains no contaminates and the paint is smooth with no scratches. In cases like these, hell, wax however you want. It won't make a difference.
Although you can get close to the sense the naked eye will never tell, small ass particles (yes, that's a technical term) will find its way into your towel, on the paint, or just simply never leave the paint. But with that being said, if enough time was spent during the prep, which consists of cleaning and polishing, whatever circle or straight line motion should not make a difference. I always wash grid pattern for obvious reasons.
Keep in mind I'm over analyzing this.