The manual shift alone will not make a difference in how fast the clutch packs grab or how much they slip. The friction modifiers in the fluid WILL affect how fast the clutches grab and how much they slip.

If you are racing then fast clutch grabs are a good thing so slippery friction modifiers are a bad thing. That is why I use Type F and not ATF+4.

BUT

There are several things inside the transmission that can affect how fast and hard the clutches grab so some transmission builders will specify certain fluids for specific reasons including softening the shift among other things.

First go by the transmission builder/manufacturer specs. If they don't have any, then I use Type F / Dexron.