The search here will pull up many discussions on 'topping' and in most you will find that yes, there are adverse effects - loss of production and stress to the plant that can have health effects.

But if 6' is your limit for some reason (I assume it is your support method?) and you don't want to grow determinate varieties that are naturally shorter plants and if you don't want the plants to just drape back down the supports as they do normally and if you don't mind the loss of production then give it a try. But leave at least 1 plant growing naturally for comparison to the ones you top. The experiment is a good way to learn what works best for you.

Dave

The later method that you mentioned of tying the plants to train them laterally is an effective way of controling height but you will need a fairly strong sopport system to hold the increasing weight of new growth and production. Often you will have intertwined growth if you train upper plants within the same row but I find that in the last month of the season this is less stressful on cherry types than lowering stems to control height with a high tunnel, stringline support system. In fact, the more intertwined the growth becomes the more the plants seem to support eachother to avoid breaking stems.