By the way, the best thing I've read on the saber forms, official or otherwise, is this Quora answer from a guy who resides about where Star Wars fandom intersects with the HEMA community (HEMA! It's like MMA for nerds!). It approaches the forms from both practical and philosophical approaches and also suggests something of a timeline and reasons why the different forms emerged.
It's pretty much my head canon on the topic.
Edited by penpenpen"Know" is an imprecise term
Most jedi would have been able to name at least 7 (at least because two variants of form 5, jar Kai, the lightsaber on off one, vapaad/juyo)
Few jedi would have mastered even 1 form
Most would know at least the basics of at least 6 (at least because again 2 variants of form 5, jar kai, etc.)
Most jedi would have been proficient in at least 1 and niman would have been the most common at the arena scene though it probably wasn't a majority.
The number of forms most jedi would have been at least proficient in is likely 1, though a significant minority would be at least proficient in more than one.
Edited by EliasWindrider“Master” is also an imprecise term.
Highly variable too depending on the school and system.
Knights of Fate has an excellent discussion on this very topic.
In small part, it says it was typical for Jedi to develop their own unique style of lightsaber combat from studying the six forms (juyo usually being forbidden). Even if focused on one style they would typically incorporate elements from other forms.
And in typical FFG Star Wars fashion it says you can narratively alter the forms to your tastes. That studying a form may mean that’s just your personal style or approach or that you are actually a practitioner of the actual Jedi form (you survived the Purge, have a mentor or a holocron). Basically you can do whatever you want and have fun with it.
It’s very well written.