What are the advantages of using different modulation techniques in an RF network?

There are AM, FM, FSK, QPSK, OFDM modulations. Actually, any modulation uses analog carriers and the wireless transmission is always analog (RF signal waves).

Digital Modulation does NOT mean it goes also digital via wireless carriers (these are always analog). Digital means "just": you encode the digital bits to be carried over analog waves (see (Q)PSK, FSK, esp. COFDM).

Digital modulation is a bit confusing as it relates to the nature of the signal before and after modulation. Impressing digital information on wave forms opens up opportunities for compressing information that wouldn't be possible if the information stream were analog, as in the case of audio signals.

The main tradeoff is between performance on a clean channel vs. performance on a dirty channel. Dirty channels want more redundancy and more robust signaling, but clean channels can use more efficient modulation and encoding.

Two important things to consider in a trade off scenario in my view are; Some modulation techniques are more robust against noise and interference than others. By choosing the right modulation, we can enhance the network's resilience to signal degradation, making it suitable for challenging environments. Secondly, lower-order modulation schemes provide better coverage and longer-range communication due to their improved tolerance to signal attenuation.

A higher data rate needs first of all a higher frequency (e.g. UHF or even light). Sure, bandwidth matters as well, more in terms of the width of the channel spectrum (e.g. spread spectrum, COFDM with a wider channel spectrum). Power consumption? on the receiver side (not really true), on the transmitter side - for sure, e.g. wider spectrum (bandwidth), higher frequency. Error Correction (e.g. to send with error correcting codes), to transmit via OFDM, to do a "channel estimation" on receiver side is a higher complexity. But this complexity supports to receive still signal even they seem to be disappeared in noise (Shannons information theorem).

Wrong! "higher modulation techniques can be used when the signal strength is high and the interference is low, ..." WRONG! Higher modulation schemes are used for better error free transition over noisy and fading wireless links, as well as for situations with multipath receptions (e.g. interference due to reflections). Also: reception done in moving vehicles (e.g. cars, airplanes, ...) need a better modulation scheme. Look at COFDM, ATSC, ... why they were invented.

All these tests needs real conditions or a "channel simulator". Esp. the testing for multi-path reception, reception done in fast moving vehicles (doppler effect) needs dedicated test setups (e.g. COFDM reception in racing cars, high speed trains, airplanes or even rockets).

More data in the same bandwidth, or over coming impairments are two major reasons to use one modulation form over others. Digital can be received in some environments where analog cannot.