Simplest/best way to control a set of 8-10 PWM signals from a smartphone
HC-05 is rated to about 9m so it wouldn't necessarily meet your requirement. The ESP8266 (example of one implementation called the Node MCU) can output PWM on any of the 0-16 pins. It can easily implement a web server which would let you control your outputs via 8026.11 (wifi). It also means you don't need to build anything for the phone/ tablet/ PC just use a web browser. The duty cycle could be set through the web server on the ESP. The ESPs are around the same price as an Arduino.  

I've used the HC-05 with an arduino. It works very well, though not very far. For the Android side I used app inventor which is extremely easily to use for bluetooth.