I played the game on a CRT monitor back in the day, would like to emulate that look. You’re correct, there were no visible black bars on VGA PC monitors.
The screen was fuzzy so it actually looked a lot better than it does in an LCD monitor due to a natural “aliasing” effect from bleed/blur/glow.
I know video game emulatores like MAME have good ones but didn’t know there was a filter for DOSBox, will try that!
Game is VGA only. VGA did line doubling. There are no black bars every other line people mostly associate with using CRT TV.