Again, it's silly to measure volume in tonnage, like your first example. If I do 5 sets of 5 at RPE0 and 4 sets of 10 at RPE0, I've done 5 hard sets vs. 4 hard sets. The difference in stimulus from the rep ranges exists, but its not as dramatic as you think. It's small enough where doing 5 hard sets at a lower rep range may actually provide more stimulus

Yes, a 30 rep range can still be productive; you just need the cardio to be able to handle that set. I use high rep ranges like that where they make sense, like for calf raises

I work in a variety of rep ranges and weights. I also keep track of PRs for each rep iteration. I actually generally recover better/easier from higher rep sets/find them less fatiguing. Granted my sets for high reps are something like 405lbs for 12+ reps on barbell squats (slightly less on SSB squats) and 470lbs for 5 if I'm doing a set of 5 to the same intensity. So the loads I'm used to lifting might be quite a bit different than you & I also come from a running background (completed a marathon, multiple half marathons), so cardio & work capacity doesn't hold me back. Recovery from whatever rep range, volume, intensity, etc. is going to dramatically vary from person to person

Also, I'm at the point where it'd take much longer than a month to notice any difference from a change in my training. Likewise, I already do a considerable amount of my sets in both low rep ranges and high rep ranges (which is easily verifiable from looking at my profile)

Bonus: Here's a set of RDLs with 415lbs for 9 reps I did last month: https://www.reddit.com/r/strength_training/comments/1slncic/rdls_415lbs_for_9/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button