score:4
1.
From National Railcards & Gold Cards on the TfL website:
If you are eligible to buy one of the following National Railcards:
16-25 Railcard
[...]
You can get:
- Discounts on some off-peak travel on Tube, DLR, London Overground and National Rail services in London
Not buses.
2.
From Bus and tram on the TfL website:
[no mention of railcards]
So, no.
2 second part.
No. The price level of the daily cap is reduced because of your discount, but what the cap covers is the same.