Hello, recently I bought a new laptop with a decent performance. (i7 3ghz, Nvidia 650m), so I decided to try ENB on my Skyrim.
When I use wrapper version (with d3d9.dll) the performance is awful (10-20 fps), but when I use the injector I get 30-40 fps with the same quality. However the injector application is very buggy, it crashes my game every 10 minutes (after 5 minutes smooth gameplay I get artifacts, then the game crashes and I have message, which says that the video driver crashed and it recovered successfully). I installed dozens of drivers and different ENB versions, but the results are the same.

I don't think it the injector leading to these crashes...

Injector is activated only at game start, so what you say is not injector bug. Nobody can help with this, it's bethesda game.

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i5-4690k, 16Gb RAM, GTX 1060 6Gb, X-Fi Titanium, Win7 x128
I am INFP, not the brutal, godamnit.

But the crashes appear when the game is started with the injector. With the wrapper there're no crashes.
Also why is the performance difference between the two so big?

You got laptop and don't know what is it? Okay, let me explain. It have on CPU integrated GPU crap, when using wrapper it activating by default. When using injector, NVidia card is used. Why? Because of NVidia Optimus programmers who too much lazy to make wrappers compatible. Why it crashing, not ask me, some users plays entire day, some similar to you, just uninstall all games by Bethesda and be happy.

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i5-4690k, 16Gb RAM, GTX 1060 6Gb, X-Fi Titanium, Win7 x128
I am INFP, not the brutal, godamnit.

уверен что настройки идентичны ?
если установлен антивирус, проверь чтобы он не блокировал инжектор