Re: What are the Battle Pass Legend Bonus mechanics?
Well they are actually "bonus" points - they're even called that: "legend bonus" (e.g., Gibraltar bonus at end of gibraltar match). All points that don't go to account level and just count towards battle pass are "bonus".
There are 3 types of bonus points (that go only to battle pass progression, but not account level):
1) legend time xp bonus (equals time xp of the match), if the weekly limit is not exceeded for that legend
2) legend daily first kill bonus (+500, once per day for every legend)
3) play with friends bonus, if any are unlocked (time xp multiplied by % currently available)
P.S. All normal leveling xp always counts towards battle pass progression too.
Also, @Geryth you can see current status of your weekly legend bonus points in the Battlepass tab (when you click on the legend icons in the corner). Should be XX/50000 for all legends, where XX - is your already accumulated points.
I'm not sure if there's any way to check the daily kill bonus status.