clutch

As with a lot of things there is always more than one school of thought. I'm a strong supporter of using the chain tensioner. If installed and aligned correctly they help guide the chain onto the rear sprocket and give you easy adjustment when the chain begins to wear (some call it stretch but it is actually wear that makes it loosen) Here is a good fix for the tensioner bracket coming loose and rotating into the spokes. We all know how dangerous and expensive that can be. You can use a bolt and nut, no bigger than a 10/32 bolt, or as some do you can use a self tapping screw at the point detailed in the attached photo. Either way you need to take special care to get the tensioner wheel perfectly aligned with the chain path and rear sprocket before drilling. Often this requires putting the bracket in a vise and giving it a slight twist to get the correct angle of the wheel in relation to the chain path. Most bike chainstays have an angle incongruent with the motor drive chain so clamping the tensioner to it without this twist will result in misalignment. Good luck with your choice.
Tom