I am part of the guys who read a lot on your forum because I find all the info I need and never comment

But today I am totally lost, and it could be great if you can give me expertise on that issue. Maybe it's only me and I should be happy about what I have. Anyway you will tell me.
Here is my spec :
- N64 PAL - NUS-CPU P-02 - Board N64 RGB Advanced - Mario 64 PAL
- Universal Nintendo PACKAPUNCH RGB SCART cable - OSSC - Profile from FirebrandX
- TV OLED LG C9
Here's a test with the PAL Snes, I can get an excellent picture. Strange that the PAL Snes provide a picture in 240p. But ok ! (Forgot to put the scanlines when I took the picture, SHAME ON ME !) Here's a test from a PAL Wii, I can get also an excellent picture. Again something strange, it provide a picture 576p when I put as setting 480p. But ok AGAIN ! I don't want emulation :/ This was only to show you that I can get the resolution we want with this TV for the N64.
Now let's go on the N64 PAL so 288p. I can get a picture with the profile of FirebrandX until Line x4 with the OSSC. The issue is, the picture is disgusting. I know that the picture from a N64 will never be excellent, but I am sure we can get better than what I have right now. All the line double from the OSSC makes the picture disgusting of the menu of the N64 Advanced and IG. The best picture overall I get is from the passthrough which I am sure there is something wrong.
Here's a test with x2 (OSSC 288p x2): Here's a test with x3 (OSSC 288p x3): Here's a test with x4 (OSSC 288p x4): Here's a test with Passthroug (OSSC 288p): Now, I want you to see when I try to put the double lining from N64 directly. I thought it would be a good solution for my issue but it's unplayable. And it doesn't even change the resolution of my TV. The console says that in Output it's 576p, but in reality, I am still in 288p resolution on the OSSC. (No black screen of changing resolution when I do the manipulation)
Here's a test with Passthroug (Double lining from N64) : Here's a test with x4 (Double lining from N64) : All the others are the same (x2,x3). It's disgusting.
In conclusion, here's my questions, why can't I use the double lining from the console ? The cable that I use is not good enough ?
Do you think I can get a better picture ? If yes, How ? Maybe the profile of FirebrandX is not good for PAL ?
I am lost :'( Please help me, it's my favorite console and it's this one that i can't get a playable picture.
Thank you,
Yelko