I have one very similar. What I found wrong with it was the "chuck" for holding the bits are only 2 set screws (on mine anyways...). One on the shaft, one holding the bit. This allowed a major wobble in the bit due to play in the diameter of the shaft/chuck/bit, making it rather useless for fine things like isolation routing on a PCB. Even with 2 opposing set screws, you still get wobble in the side direction. What I ended up doing was ordering a small adjustable "drill" chuck on Ebay, with a press fitted brass bushing over the shaft (heat the bushing and slide on, then cool). The adjustable chuck is much more stable (straight) than what they supply. These chucks are made for these hobby milling machines.
Other limitation was there are no limit switches. If you have to reset while doing some milling, you cannot necessarily find true "zero" again, without some form of limit switches (optical are best, micro switches next best). The controller has inputs for limit switches.
Your controller board is a little different than mine. On mine, there was no PWM for the spindle motor, only for the "laser" output. On mine, the PWM would only work when it was high enough to trigger a relay to turn on the spindle full power. I worry about that relay on yours, it may be the same "idea". You can easily tap into the PWM signal and feed a MOSFET driver to get true PWM speed control on the motor. BTW, my motor is not a real high speed one, and not very high torque, but enough to mill things like PCBs.
Finally, I found the gantry too low, mostly due to the extra chuck length. By the time I added a sacrificial board on the table, the limit of vertical travel (Z axis) was less than 1/2 inch. I ended up ordering new aluminum frame members (they come in 3 foot or 6 foot lengths from CNC shops), and extended the height that extra 1/2 inch+ (with spare length on top in case I mill something thick and have to raise the motor).
Check the firmware in the controller. If it uses GRBL firmware, download the latest version (1.1f?) and flash it.
https://github.com/gnea/grbl/releases
Those are my comments. You may find your model has some slight differences or features fixed (or different ones broken). Good luck and have fun with it...
EDIT:
PS: if ordering frame members, check out their 90 deg angle brackets. The grey items in your picture are plastic (including the motor mount), and that 45 deg support on the sides does not provide the best support. Using steel 90deg brackets on the outside (horizontal side to vertical member) locks it in a lot better with less flexing.