This review and meta-analysis analyzed the effect of resistance training performed until failure with low, moderate, and high loads on muscle hypertrophy and muscle strength in healthy adults. It also looked at the possible participant-, design-, and training-related covariates that may affect hypertrophy and strength gains. The final analysis included 24 studies examining hypertrophy and 23 examining strength. Combined, the studies included 747 participants with an average age of 23.4 years (a mix of untrained and recreationally trained).
For muscle hypertrophy, it did not matter whether the participants completed high, moderate, or low-load training. For strength, however, both high and moderate loads were superior to low loads. High load is likely superior to low load but the results did not meet statistical significance (p=0.068). Keep in mind, the load refers to the amount of resistance, not the volume. Low load is an intensity of <60% 1 rep max or a 15 rep max, moderate is between 60% and 79% of 1-RM or 9–15 RM), and high is ≥80% of 1-RM or ≤8 RM.
This data, along with similar reviews, suggests the amount of resistance is not important, provided the participant is training close to failure. A 2 RIR set of 8 is equivalent to a 2 RIR set of 15. If the intensity (e.g. RIR or RPE) is equivalent, then training volume (number of total sets) is the primary driver of hypertrophy. For strength, low loads are likely inferior. Of note, a 1 rep max testing is a skill. If you want to improve your ability to perform a max effort lift, that needs to be trained. A 10 RM, even to failure, is not the same as a max effort. This is important for your return to sport phases of rehabilitation. You need to replicate max effort activity to prepare the body and mind for the demands of a sport.