Samsung NX300 has a
20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features DRIMe IV processor. On the other hand, Fujifilm X-A3 has a
24.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features EXR Processor II processor.
Below you can see the NX300 and X-A3 sensor size comparison.
Samsung NX300 and Fujifilm X-A3 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Samsung NX300 has 20% larger pixel area compared to Fujifilm X-A3, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.