The Dayton Audio iMM-6C plugs into the phones USB-C port, as
@bernard23 said. It contains its own ADC. The iMM-6 has a 3.5 mm TRRS plug, so you either need a phone with a matching jack or a USB adapter that supports microphones (not just headphones).
Oddly, the calibration files for both mics that have been posted here seem to indicate, that the analogue iMM-6 shows etter linearity, especially in the bass region. Calibration files are intended to correct such non-linearities, but as of now the WiiM Home App does not support to import such a file.
The measurement looks very good to me. That peak at 8 kHz can savely be ignored. As
@Emiyanez pointed out it's an artefact created by your phone's built-in mic. It's one octave above the default correction range, soo it doesn't matter at all.
Why did you choose to not include the subwoofer? Since WiiM do support this now I would suggest you try it both ways and just stick with what you like better.
The same goes for the frequency range of correction. As has been said, correction at too high frequencies might give good looking results, but moving your head (or the mic) just a few inches might result in a totally different frequency response.
Personally I think that correction up to 4 kHz can work, depending on boundary conditions. It's just not the most important range for improvement. However, if you like what you hear as a result, then there's nothing wrong with that. You could take some more measurements in slightly different places and see where the results start to differ. You might then restrict the correction range to frequencies below that point.