DSP-enabled multi-channel aggregation techniques are promising for cost-effectively improving the flexibility, adaptability and elasticity of fronthaul transport networks. By utilizing orthogonal digital filtering in multi-channel aggregation in IMDD transmission systems, two DSP-enabled matching filter (MF)-free multi-channel aggregation techniques respectively based on SSB OFDM and orthogonal DSB OFDM have been reported, the SSB (DSB) technique has, however, a drawback of relatively high digital filter DSP complexity (reduced adaptability to physical layer system characteristics). To effectively overcome these drawbacks associated with these two techniques, in this paper, a DSP-enabled MF-free adaptively variable SSB/DSB OFDM multi-channel aggregation technique is proposed and experimentally demonstrated, in which >72Gb/s@25km IMDD transmissions have been achieved. This work also evaluates, for the first time, the flexibility, adaptability, and elasticity of the orthogonal digital filtering-enabled multi-channel aggregation techniques. The results show that the proposed technique not only maintains the SSB technique’s excellent adaptability but also possesses the DSB technique’s low digital filter DSP complexity features.