Less intense, longer duration (more TSS is not intentional, just comes with longer duration)
For example, last week substituted recommended Town Hill (IF 0.69, TSS 129, 2:45) with Allegheny (IF 0.68, TSS 151, 3:15). Didn’t feel much difference during next VO2max workout after the recovery day. This week will try Rafferty (IF 0.65, TSS 157, 3:45).
Can’t say if it improves fitness better or worse. According to FTP prediction model, my improvement is exactly what is predicted, even with those changes.