Same thing, MacBook Pro 10,1, OCLP 0.5.2, dGPU disabled (dead 650M), using HD4000 with NVDAResman and NVDAStartup kexts loaded to enable screen brightness control. Not sure, but GPU might be somehow relevant to this issue.
Safari 16.1 is almost unusable on YouTube. Disabling all extensions and clearing cache doesn't change anything. Disabling YouTube's "Ambient mode" (as I saw someone suggested) also doesn't help. Switching quality down to 360p helps a little, but CPU usage still stays high. And there are many sites that started to use too much CPU, it's not just YouTube.
Invisible Google results in the dropdown can be fixed with custom CSS:
CSS:
body, input, button {
font-family: "Arial Unicode MS", sans-serif !important;
}
The default Google's CSS uses Arial and sans-serif, and Arial is a problem. You can just remove it in CSS (in Safari Web Inspector) or change to any non-existent font name like Arial123, and search results instantly becomes visible. There is a /System/Library/Fonts/Supplemental/Arial.ttf file in Monterey 12.6.1 (and Arial font is listed in the Font Book app) but it looks like Safari can't use it properly. Another possible fix which doesn't require use of any extensions, might be:
Bash:
ln -s /System/Library/Fonts/Supplemental/Arial.ttf /System/Library/Fonts/Arial.ttf
But I haven't tried it.