Nikon D7100 has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor . On the other hand, Fujifilm X-T30 has a
26.0MP APS-C (23.5 x 15.6 mm ) sized X-Trans CMOS sensor and features X-Processor 4 processor.
Another similarity between these two cameras is that both Fujifilm X-T30 and Nikon D7100 sensors lack anti-alias (Low-Pass) filters. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the D7100 and X-T30 sensor size comparison.
Nikon D7100 and Fujifilm X-T30 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 Nikon D7100 has 8% larger pixel area compared to Fujifilm X-T30, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.