An i3 is amazingly powerful, especially with small to medium libraries and DSP to just one or two end points. An i7 will be needed for much larger libraries and more extensive DSP (more endpoints.
Since you did not mention a library of 100,000s of tracks or a desire to use HQPlayer, I can’t imagine what advantages would come from an i9.
The major versions you’ll see used are Intel NUC8ix boxes in the short BEH or tall BNH configurations.