I’ve had multiple cars and vans with dreadful headlights and I’ve always fitted whatever people recommended as the best bulbs at the time. Usually Nightbreakers.
I think the best I’ve managed is a slight colour improvement where new bulbs might be whiter than yellowy older items. My T5 was terrible even with the supposedly illegal, unrated rally bulbs. The Panda 100hp went from yellow to white with Nightbreakers but not any brighter.
I’m no auto electrician but I feel like if you headlight loom can’t deliver enough juice you’re stuck with dim lights.
It’s much worse these days when someone with modern superlights comes up behind you and casts a shadow right in front of you where your own illumination should be.