I have two questions:-
1) A girl was talking near a group of kids. The kids were a bit scared of that girl. Also that girl was very beautiful. When the girl left they started talking about that girl. Will they say:-
"That girl was very scary" "I know, however she was quite remarkable" "She was very beautiful"
"That girl is very scary" "I know, however she is quite remarkable" "She is very beautiful"
I know that the girl left so you can use "was" because they are talking about a girl who is no longer in the room.
However if there is an object which looks very beautiful and after that the object became ugly then you will say "that object was very beautiful" and the was here means that the object is no longer beautiful
2) In the past a girl played against an opponent and that opponent is a beginner so she took it easy on that opponent. After that the girl talks about that match. Will she say:-
"In the past I wasn't hard when I played against an opponent who is a beginner."
In the past I wasn't hard when I played against an opponent who was a beginner.
I know the match is in the past so when she is describing the opponent that she played against she can say "who was a beginner"
However if there is a person who is a beginner and then that person became an expert then you will say "that person was a beginner" and that means that the person is no longer a beginner
Is using was or is both grammatically correct in the two examples in what you want to use is up to you?