There isn’t one universally “best” mode for macro here—it depends on which gives you the results you want.

TTL is a good starting point if it gives you consistent exposure and saves time. That’s what it’s designed for.

Manual flash is the better choice when TTL isn’t giving reliable or repeatable results, or when you want full control. In manual mode, adjust flash power, flash zoom, and the flash-to-subject distance until the lighting looks right.

A practical approach is:

• Start with TTL for convenience.
• If exposures vary too much or the lighting isn’t what you want, switch to manual.
• Once your setup is fixed, manual often makes it easier to keep results consistent from shot to shot.

So: use TTL if it works well for your setup; use manual when you need more control or consistency.