JF-17 B was developed for fighter conversion requirements of some export orders however it doesnt make it a training only jet. It has full combat capability. Advent of advanced simulators have reduced dependence on twin seat fighter converters for PAF so for fighters PAF uses the twin seat version in same roles as the single seater when they are not in use for conversion training. The F-16B/D have been valuable strike aircrafts for PAF in anti militant operations as the second pilot can concentrate more on finding hidden targets using the targeting pods. Same role is envisioned for the JF-17B. Second seat pilot is also very useful in dedicated EW missions as he can operate as a signals officer and select what measures needed to be taken for active jamming, same role can be done by single seater but added workload on pilot.
Aircraft pylons can be installed as per requirement. There is a wide variety of options and types depending upon the load out that needs to be attached eg, multi ejector racks, for fuel tanks, for AA missiles for, for pods etc.
The picture you quoted is a JF-17B in clean configuration and eventually once it enters operation there will be more pictures of it with loadouts.
Here is a JF-17A Blk-2 in clean configuration and then a picture with pylons and weapons. Pylons are usually removed from aircrafts when performing displays in order to minimize drag. Wingtip pylon on the thunder is built into the aircraft wing, its usually done for aircraft where some type of ECM equipment or sensors are on the wingtips.
Infact a new multi pylon for SD-10 loadout is expected for JF-17 Block-3
Here's a picture of a twin seat Rafale in clean configuration, it doesnt make it a trainer only
Also you see the needle in front of the nose of JF-17B, this means this is a test aircraft. It's used for recording parameters. While most of these sensors are integrated into the aircraft for service, having them on a boom in front of the nose keeps them in undisturbed airflow to provide exact data which is used to check how well the aircraft behaves compared to design predictions/ parameters.
YF-22 test unit with similar sensor, its a norm on all test units.