If you want topomap, that’s the correct function. Provide data as an array of shape (n_sensors, ) (one value per sensor location on the topomap) and pos as an mne.io.Info instance that contains the location/montage for all sensors.
You can create the info with mne.create_info and then add the montage with info.set_montage().
https://mne.tools/stable/generated/mne.Info.html