There is a sticky on the subject.
I have seen that melted headlight harness more than once.
You do not need over wattage bulbs to melt that harness. The stock bulbs can melt it just fine.
A premade relay harness is a good way to go, though the prices of them have come up in recent years. Still a good investment.
The headlight lenses need to be perfectly clear to work correctly. If the damage is not too bad, the Sylvania headlight restoration kit works very well, its not just good, if the headlights are still salvageable, you can restore them to a like new condition. And because the Sylvania kit replaced the damaged clearcoat with a new one with UV blockers, the restoration lasts a long time, unlike the cheap polishes often touted as a restoration, which has temporary results, but fades quickly, often allowing new damage to go deeper, ruining the lens permanently.
Sometimes the stock reflector can oxidize, if that happens the whole housing needs to be replaced. Most aftermarket lenses use cheap coatings, so it wouldn't hurt to use a Sylvania headlight restoration on a new headlight. Since the new light will already have a finish on it, you just need to quick wipe it with denatured alcohol to remove any oils from the surface, then apply the Sylvania Sealant over the lens. This will prevent it from degrading from day 1.
The relay harness mostl reduces the resistance which causes voltage drop, which makes the headlights not produce full output. Voltage drops cause an exponential decrease in light output, and most headlight bulbs are rated at 13.8 volts.
If you do the job cleanly, you can now build you own harness for less than the pre made ones. By cleanly, I mean that no splicing in the stock wiring is needed, it can be made with plug in connectors. You can get the headlight sockets, both male and female, some ring terminals that can fit on a battery connection or starter relate post (gold plated is best so they don't corrode), a good ground, some relays that are rated for automotive use that have the proper amp ratings to handle the load. There are nice relays that come with a harness connector, so they can be unplugged and replaced.