I thought usually bags that hold 6 or more rackets typically have the double backpack type straps. I have a three pack and it has only the one sling strap. Also have a backpack which holds two rackets. Noticed men tend to use the bags vs. a backpack as their main tennis "luggage". Maybe a backpack looks too "girly"?
Discounted Prince and Head rackets, cheapest string I can get, strung at 60+ pounds, clothed in any name brand under $10.00 mixed with Target.