Classical guitar strings

I'm not aware of any classicals being so light/fragile that a set of classical strings, even a hard tension, would damage it. If a guitar is extremely light I'd be inclined to keep lighter strings on it. I usually see this with flamenco guitars more than classicals. If I put my work light in the soundhole, the guitar glows because the top is so thin!

The reason I would favor a lighter string on a lighter guitar and vice versa is in part because that is usually what sounds best. In the same way on a steel string guitar that is built like a tank you'd want mediums, and a more modern guitar that is more lightly built you'd want lights. It is rare that I'd have such an opinion based on the structural integrity of the instrument.

If you go to the D'Addario site they'll give you the tension of the individual strings in their sets, and there isn't much variation from one set to another. I mostly feel a difference in how springy they feel under my right hand as I play. I feel almost no difference at all under my left hand. For playability, setup is obviously important, but technique is often overlooked for those coming from steel string. With a giant classical neck with a flat (or near flat) fingerboard it can be easy to grab it on the wrong way that is very hard on the wrist. Finding a pleasant grip with a neutral wrist position is likely a bigger deal.

I've had a lot of clients trying to play guitar post injury, and one dilemma the end up in is going for very light strings and low action but they're still PLAYING the guitar as though it has heavy strings and high action. Think of it like this: if you're typing on a modern keyboard with very shallow, easy keys and you're still smacking them like you're using an old IBM Selectric typewriter, you'll get tired just as fast. If you want to take advantage of the lighter keyboard, you need to type with a lighter touch. Who knows, maybe you had too hard of a touch with the IBM typewriter, and switching keyboards was unnecessary! That isn't to say any of this applies to you, but it is something I've seen very, very often. I suspect a good bit of it comes from a generation where "beginner" guitars invariably were very hard to play.

Sorry, I'm rambling. Hopefully something there is useful to someone!

“I've had a lot of clients trying to play guitar post injury, and one dilemma the end up in is going for very light strings and low action but they're still playing the guitar as though it has heavy strings and high action.“

One thing I learned a while ago is to use only the amount of strength needed, I found myself tiring out or creating pain and learned to back off.  Though this initially was playing the bass it became natural for me regardless of the instrument.  A couple of years ago playing the 000-15S  night after night around campfires my hands were taking a beating. After a few nights I noticed I was using more effort than needed and adjusted. It’s easy to over do it, to slip back into bad technique.

I’ve rarely used pics, Occasionally I’ll use them on bass for a sharper attack. On the guitar I’ve tried them early on but they just seemed awkward. I’ve always played with my fingers, the only other technique I’ve ever used was the bow on the violin and concert bass. Half of my basses are fretless, I used about the same amount of fretting pressure on each type.