Tx power, Rx sensitivity, Antenna, Noise all affect range.
Antenna design, to get gain also implies reduced radiation pattern, eg.
antenna takes on directional characteristics/ Yagi's a good example of that.
This might be of use -
http://www.cypress.com/?rID=102512 AN91445 - Antenna Design Guide
Any news about it ?
Some good design examples ?
Changing the BLE module to not use low power mode may also increase range on the module at the expense of more power draw, but it might merely be related to the clock source for the BLE module.
There are two separate TX power levels for Connection and Adv/Scan separately, changing both to be higher/lower will affect performance versus power draw.
The CY5674 PRoC has an antenna port on it for use, potentially you could get longer range with antenna selection.
Dana @user_14586677 already listed the main culprits for range in wireless/RF design. But wireless propagation is difficult to comprehend and design due to 3-dimensional calculations and requirements.