Is the modulation method, or nature of modulation otherwise, between my phone and my WiFi modem, versus my phone and a cellular mast, different?
From google: 3G-5G appears to use OFDM —along with QPSK og QAM depending on channel conditions.
WiFi 802.11b used some CDMA-dialect, 802.11a and g uses OFDM along with BPSK, QPSK or QAM.
WiFi mainly use frequencies around 2.4Ghz, while cellphones have used lower frequencies around 900Mhz (due to larger distances). Both have recently added capability for using higher frequencies.