Thank you, the link is very helpful 😊.
Yes, more safe. Then to pick earliest train to olomouc the other day. Thanks for suggestions.
Could I exchange euros to Kč on board and then pay trams?
No - there is no facility to change money on board trams. it is best to withdraw some CZK from an ATM in the railway station and buy a small item in the shop so you get some change - I am sure you can also buy tram tickets there.