The WPBakery Page Builder / Visual Composer Master Course is a user focused course (as opposed to a course aimed at plugin developers building addons and integrating with WPBakery), and weighs in at around 3.5 hours of instruction.
While there are a couple of other courses on Udemy that do include WPBakery instruction, this is the only one that's devoted entirely to the plugin, the others mentioned just cover the basics in a section or two. Outside of Udemy, there are a couple of other small courses about WPBakery, but nothing that goes into the same level of detail.
The main downside to the WPBakery Master Course is that it's getting a bit old now - it hasn't been updated since 2018, and of course the world of web development moves fast, quite a lot has changed since then.
Should you buy this course? The fact that it's pretty much the only one available with this level of detail would suggest yes, it's practically your only choice, however the fact that it's so dated is not ideal. If video courses are your preferred method of learning, and you want something self contained rather than trying to piece things together from multiple unconnected youtube videos, I would suggest you do try this course, but with the understanding that you won't necessarily be able to directly translate what you learn without a little work. The WPBakery course is still good for learning the fundamentals, it's just not perfect.