Defoliate or not?

The only thing you can take off its this big damaged leaf. He has max 30% of health left and is too close to medium, so some fungus problems could start. The rest dont need anything. Less leaves - less energy is produced. Simple. What worries me tho, such compact nod spacing and early praying, maybe your light intensity is too high ?

Not at this point. Remove any damaged leaves you have. But keep the rest. The plant is still small and developing. You could remove some side shoots to help shape the plant, but I wouldn’t defoliate.

No, never. Less leaves = less energy being made = less growth.

I assume you'll be spreading that out a bit? So, kinda depends on what you want it too look like in a week or 3 etc.. Always remove as few leaves as possible. Don't just randomly pluck leaves. Have a very excellent reason to do so. Unless it's going to be a really small flowering plant, that lower shit probably won't even exist to develop buds at that point. Strip lower axilla that isn't important to the future canopy, but keep the leaves at the nodes. This will help thin it out if concerned. the stuff at the top you just keep training the branches out from each other for an appropriate amount of spacing and the leaves can remain.