I tried to do my first Wii trill but accidentally cut too far into the board. I'm not sure if I cut any necessary traces and was wondering if this still worked.
This board should still function. The main areas of concern when trimming are on the back edge where your NAND is (which isn't visible in either of your pictures) and this area near the bottom of the board:
The red line runs along the NAND traces you need to avoid going through and the blue line is how far inwards you can go before reaching them. That notch you cut out doesn't go into the red line I drew, so I believe you should be okay. Be aware of this when sanding though.
As stated above, I can't see the edge of your NAND since the picture cuts off. From what I was able to see looking at the front of the board, I'm pretty sure you didn't cut too much off, so I think you're fine. I can't say for sure though since the back of your board isn't fully shown in the picture.
I would also advise carefully removing these caps for the longevity of your console (these caps can leak acid after many years), they also tend to get in the way of providing clearance in most builds:
Thank you for the detailed response. Here are some photos of the back side. I think the rest is fine I was worried about the notch I cut. And I will remove the cap, thank you