One thing about aftermarket headlights, make sure they are DOT certified if you are going to run them in the US. Also, if the reflector isn't designed for LED or HID then you may still be ticketed for having the wrong light in the headlight case.
Head lights on cars are engineered to reflect the light from a specific source to where it needs to be on the road, down the road, to the side of the road, and above the road to illuminate overhead signs. There is a lot of science that goes into this. For example, when designing a light fixture to use with a H7 bulb, an engineer will look at where the filament is inside the bulb. This is where the light source comes from. The reflectors inside the light housing will direct that light to where it needs to go without blinding oncoming traffic, or the driver himself.
When the LED replacements first came out, they did not take into account this engineering. So when the LED bulb was placed in the housing, the light source was in a different place than the old halogen filament. The light was brighter, but it was shining in all the wrong places. If you have ever been blinded by someone running LED lights that were not engineered to be direct replacements for the halogen bulbs, this is what is happening. Now it gets to actually be dangerous, not just for the driver of on coming traffic, but for the drive himself. These lights look brighter because there is whiter/brighter light being dispersed directly in front of the vehicle. This brighter light makes the drivers pupils dilate and focus at a closer reference point, it is actually decreasing night vision down the road making it harder to see things before they are right on top of you. It also does not cast light to the side of the road as it should which limits visibility to what might be about to enter the roadway.
I'm not saying don't buy a specific product, just saying make sure that product is legal and engineered to use the light source you are putting in it.
There are a lot of good articles that explain this process on the web. Most importantly check your local laws so you don't get hassled.
You are correct, and only a few things to touch up on.
One thing about aftermarket headlights, make sure they are DOT certified if you are going to run them in the US.
The US DOT actually doesn't certify lights or create the requirements, what they have done is codified the SAE standards. Canada also has adopted these same standards. European countries have their own standards and all lights there must have the "E-Code" stamp on them. Most other countries will have either have their own or adopt one of these in some form or another.
These "certifications" are based on the type of bulb that is within it, so if you change from Halogen to HID or LED they are no longer type certified.
When designing a light fixture to use with a H7 bulb, an engineer will look at where the filament is inside the bulb... The reflectors inside the light housing will direct that light to where it needs to go...
When the LED replacements first came out, they did not take into account this engineering. So when the LED bulb was placed in the housing, the light source was in a different place than the old halogen filament.
It is not just the filament location, but also its other physical characteristics such as size, shape, length, and orientation. And it is not just the reflector that is based on this, but also the lens shape and any optics integrated within it. These 3 elements (reflector, source, lens) all work together as an assembly. Flaws or changes in any of these will more often than not have a negative impact on the light emitted.
Even dropping in some LongLife bulbs of the same type can have a negative effect; the filament often has a larger diameter and may bring in a "blur" factor. The opposite can also happen, and a bulb designed with a thinner diameter will often give a "sharper" beam pattern at the cost of a shortened life span. Needless to say; no 2 light sources can mimic each other in physical characteristics such as shape.
Tuning headlights is not much different than tuning an engine. Changing one element of the system (larger throttle body, higher wattage) cannot be fully appreciated until the other elements are tweaked for the change (higher fuel flow, larger wiring). And even if you do these compensations, can the rest of the assembly handle it- how much more heat is a 130W H1 going to generate and will it melt the plastic lenses?