Typical forming sizes for desktop FDM 3D printers are 200 x 200 x 200mm. industrial machines have larger build sizes.
To prevent warping, avoid large flat areas and add rounded corners to sharp corners.
FDM is inherently anisotropic and therefore not suitable for critical parts of machinery.
The minimum size that can be printed on FDM machines is limited by the nozzle diameter and layer thickness.
Material extrusion makes it impossible to generate vertical features (in the Z-direction) with geometries smaller than the layer height (typically 0.1 - 0.2 mm).
FDM 3D printer is usually unable to produce flat features (in the XY plane) smaller than the nozzle diameter (0.4 - 0.5 mm).
The wall must be at least 2 to 3 times larger than the nozzle diameter (i.e. 0.8 - 1.2 mm).
If you wish to produce smooth surfaces and exquisite models, you can have additional post processing, such as sandblasting and machining, may be required. An alternative AM technique like SLA may be more suitable for this situation.