Experiments have found that training to failure and training close to failure produces the same hypertrophy when the volume is the same. The strength however had increased more in the close to failure group.
This seems to indicate that the close to failure group had less fatigue and could have done more volume in which case they should have gained more hypertrophy than the to failure group.(1)

Further when doing compund movements such as the squat you can train further away from failure than when doing isolation exercises.(1)

So for isolation exercises you should have 2-3 Reps In Reserve (RIR) except for the last set where you go to failure. For isolation exercises with lighter weights in the context of bodybuilding pretty much every set should be to failure (2).

For compund movements you can have higher RIR. You can start with a high RIR (say 10) and decrease this as you work up to your top (heaviest) set where you have 1-3 RIR. 
However there are probably individual differences here. Many respond well to volume whereas some respond better to training to failure.



As a sidepoint there is a lot of bad information in fitness videos on youtube. That someone is knowledgable does not guarate the quality of their content. Sadly the youtube money per click model favors entertainment over education and volume over quality.
For instance Jeff Cavaliere has more than 1300 videos on youtube and more than 2.2 billion views. He has been called out on using fake weights and contradicting himself from video to video.

I would suggest you instead watch videos from these guys:
- Layne Norton
- Mike Israetel
- John Meadows   

Further if you have not already done so I would suggest you read one or more books on strength training.
I can recommend:
- The Art of Lifting (Nuckols and Isuf) 
- Maximum Strength (Cressey)
- The new rules of Lifting (Schuler and Cosgrove)

One important takeaway from these books is that one should prioritize compund movents such as squats, deadlifts, push-ups and pull-ups that train many muscles simultaneously. After having completed these one can use isolation exercises to hit the remaining muscles. 
If one do it the other way around and start with the isolation exercises (small pebbles) there may not be "room" for the compound movements (big rocks):
[![enter image description here][1]][1]

(1) [Why Training to Failure Might be Limiting Your Gains][2]

(2) [Why You have Little Biceps ( Intensity )][3]


  [1]: https://i.sstatic.net/yfFsl.png
  [2]: https://www.youtube.com/watch?v=En2j0BK3IJQ
  [3]: https://www.youtube.com/watch?v=50kJ8HdLxs4