Whether recording emulated old console games like DS, Wii, or GBA carries legal or YouTube strike risk depends on how you obtain the game files (ROMs).
Download ROMs you don't personally own is illegal piracy, which could lead to legal action or copyright takedowns. However, playing and recording ROMs ripped from your own legally acquired copies of those games is generally considered lawful in most regions.
Platforms like YouTube may still have specific policies around copyrighted content, so be sure to check their terms of service and avoid using copyrighted music or assets in your recordings. Always err on the side of caution and prioritize legal game acquisition to avoid potential issues.