use of doing away with sets and just performing repetitions with more frequent fixed rest

For health-Related Fitness, the external load training strategies typically recommend performing 1 -2 sets of 8- 12 RM with 2 – 5 minutes rest between sets. Emerging evidence supports the use of doing away with sets and just performing repetitions with more frequent fixed rest intervals of < 30 sec) (ie every 3 reps) or random rests intervals < 30 sec ( whenever a person feels tired or the form is poor). Which approach would be more effective for health-related fitness and why?