There are 3 levels of quality for SNK emulation on PC:
1. Basic Dotemu aka ROM dump
2. Advanced Dotemu (has some more effort put in, standard-looking main menu, sometimes online features, leaderboards, achievements, more options, etc)
3. CodeMystics (much more effort put in, more options, correct scaling, much better online netcode, backgrounds, galery and other extras, etc).

Sengoku3 port by Dotemu is unfortunately just the very basic emulation version, not many graphics options included (windowed mode which is not correct resolution for proper pixel scaling) and fullscreen that is blurry (unless you maybe create custom resolution that integer scales from 320x224). There is no option for scanlines either.

Your best solution for Basic Dotemu versions is to take original ROMs after installing the game and play them in some better and more accurate emulator, that supports correct pixel scaling and scanlines.

Alternatively if you want to use dotemu emulator, then maybe try to use some custom resolution and game running in fullscreen that is not blurry and maybe add scanlines with some simple overlay app, if Reshade doesn't work for you. E.g. like this Scanlines for Windows.