It’s really not as convoluted as the optimizers are making it look. For the most part it works the same as it does in the 2014 rules. Attack with a Light weapon: get another attack with a different Light weapon as a bonus action, don’t add ability mod to damage on the second attack unless you have the two-weapon Fighting Style. What’s new is that if you have weapon mastery with a weapon that has the Nick mastery (so, dagger, light hammer, or scimitar), you can make the second attack without having to spend a bonus action, and now the dual wielder feat lets you use a bonus action to attack with any one-handed weapon after attacking with a Light weapon, instead of allowing you to use the two-weapon fighting rules without the weapons needing to be Light. Nothing about that is particularly difficult to understand. People are just trying to figure out how hard they can exploit the specific wording to sneak in an extra attack, or to juggle weapons between one hand and their belt to “dual-wield” whilst holding a shield the whole time. Most of this is actually a result of the rules for drawing and stowing weapons being much more generous now, not the various features that enable dual-wielding. Also, trying to rules lawyer the wording of rules we’re getting secondhand is extra tricky.