Hi Michael,
Within zones 1-6 the price of travelcards is generally more than the caps as a way of persuading people to use PAYG. This means you only pay for what you do which often works out less than a travelcard. If you do exceed the cap you’re still better off. Beyond the zones the caps are set at the current day travelcard prices because using PAYG is seen as a convenience rather than a cheaper option.
At the moment you can’t add railcard discounts to contactless PAYG, and there’s a question mark over whether the Network Railcard will be possible when TfL introduce a card to allow discounts. The problem is the minimum fare on weekdays.
There have always been maximum journey time restrictions when using PAYG. Anyone making a normal journey will not be affected by this unless a problem occurs en route. Enthusiasts can sometimes fall foul when they spend longer in the system than usual.
PAYG prices and caps from Slough are valid on both Elizabeth line and GWR.
Alan: There is no afternoon peak on off-peak caps either. The single fares may be higher, but they’re still limited by the off-peak cap.