The moderator ruled out paradox at once, because it could consume the panel.
One panelist really disliked the way the authors so seldom came to grips with the question of freedom vs. determinism.
Can you change the past? There's the branching universe one, where you're free as a bird, which kinda means no control. One panelist sticks to a block universe --- what happened, happened. Much discussion of what happens between the lines. Much more skill in interpolating what you want in between the known facts of history. Much more artistry and adventure. One panelist had written a story in which the main character came to learn she could change the past.
Some talk about the making literal of non-linear storytelling -- which is what time travel does, just like SF and fantasy make literal so many metaphors and literary techniques.
The amount of research to get history accurate, which can be crucial.
The moderator asked why they choose time travel as a thing to do. One was talking about the futuristic society she wanted, but people were dissatisfied because that, in itself, didn't need time travel, just the setting. Me, I missed a far amount of the answers, because I was thinking of my time travel story and the reason was that I needed a problem for the heroine after the inciting event, and once I realized that if one thing took as much time as it needed, it would mean another had gone stark raving mad in isolation, so I had to make time not match up for that, and it proved a lovely problem thereafter. 0:)