Usually, no—you should not assume a film emulation preset expects you to manually set WB to daylight first.

Daylight-balanced color negative film such as Portra 160 is normally color-corrected during printing or scanning, so the final look of real Portra is not just the raw film response under daylight. That means a preset trying to mimic Portra may already include its own color assumptions, and adding a daylight WB beforehand can push the file too far and make it look cooler than expected.

Also, in RAW processing, “daylight” is not always a simple fixed Kelvin value; converters may also apply tint shifts on the green/magenta axis. So setting 5500K/daylight and then applying a preset can effectively stack corrections.

In practice, the best approach is to treat the preset as a starting point: try it with your normal or auto white balance, then fine-tune WB afterward by eye to match the look you want.

If this were slide/reversal film, matching the film’s native balance would matter more, because there is no print/scan color correction step in the same way.