What I learned after switching to extra super light guitar strings
The lightest guitar strings I've ever played was a 7-38 set a really long time ago by a brand I don't even think exists anymore. And by really long time I mean over 20 years ago.
The only "standard" 7-38 set I know of now is the Dunlop RWN0738, otherwise known as the "Reverend Willy" set. Have I tried that 7-38 set? No, but maybe I will someday.
Why did I switch from 9-42 to 8-38?
First, since I started playing a Jazzmaster, I switched from heavy picks to medium and thin picks to avoid knocking strings out of the string saddle grooves. And even though I'm learned enough with Jazzmaster to where I could use heavy picks without knocking the strings out now, I've grown accustomed to the thinner picks. Rarely do I use heavy picks these days.
Second, on the rare occasion I do use a heavy pick, I find it dulls the sound of the string. I get the most attack and treble response when using thinner picks on thinner strings.
Third, I don't bend strings nearly as much as I used to, so I don't need the thicker strings for longer note decays with bent notes.
Fourth, the Jazzmaster (and Jaguar) by nature does not have long note decays anywhere on the fretboard. Not with the traditional bridge and saddle setup, anyway. If I wanted "sustain for days", I'd just use a Telecaster. Yeah, I could get long note decays out of a Stratocaster, but it's easier on a Tele. Since I'm not looking for long note decays because that's not the Jazzmaster's strong suit, using extra super light strings is just fine.
There are other reasons I could list but you get the idea.
Lessons I've learned from using extra super lights
Lesson #1: Difficult to find locally
I have a major Guitar Center and Sam Ash about 30-ish minutes away from me. GC never has 8-38 strings in stock. Sam Ash does, but darned few to choose from. Ordering strings online is something I do regularly now.
Lesson #2: Takes longer to stretch out
For whatever reason, 8-38 takes longer to stretch out compared to 9-42. Couldn't tell you why.
Lesson #3: Lasts longer than 9-42
I rarely snap a string these days, so I usually only change a set either when strings start losing tune all the time and/or rust and/or dent. 9-42 sets do lose tune and/or rust and/or dent faster than 8-38 sets do. Why? I have no idea.
Lesson #4: Weather changes affects the neck more
8-38 has less overall tension on the neck than 9-42 does, so when there's a significant shift in humidity (like a rainstorm that comes by), that does have a more noticeable effect on how the guitar plays.
Lesson #5: Better treble response
Thinner picks helped get more treble response, and switching to extra super light strings helped even more. Thin picks + thin strings really work well together.
Am I telling you to switch to extra super light strings?
No, because they're not for everyone.
The only thing I do suggest is not to purposely punish yourself.
What I mean by that is that some guitar players use certain types of strings because of bad advice they shouldn't have taken in the first place.
For example, many heavy metal players sincerely believe super-thick strings are the best things to use for solos. That's nonsense. Yngwie Malmsteen's set is 8-11-14-22-32-46. I don't like Yngwie's music, but the guy can obviously solo very well and he doesn't use thick strings. The only string that qualifies as "normal" is the low E 46 thickness. All the rest are very close to an 8-38 set.
Then there's Hendrix. I don't like his music either. But he used 10-13-15-26-32-38. Again, no super-thick strings here.
For whatever string thicknesses you use, it should be something that makes your guitar as easy-to-play as possible. "Working through the pain" to bend notes on thick strings is REALLY STUPID because the only thing that leads to is hand injury.
If thick strings cause you any hand, wrist or finger pain at all, switch to a lighter string. Don't think about it. Just do it. And if you have to custom create 1 set from 2 different sets of differing thicknesses to get just the right feel, then spend the extra cash and go for it.
I get along with 8-38 and plan on sticking with it as it suits me fine for what I play these days. I'm not saying you should use 8-38 like I do. Use whatever you like. But I do recommend trying 8-38 at least once just to see how it feels.
As for the 7-38 (which is a 7-9-11-20-30-38 set by the way), it's like I said, I've not tried it, but one day I might.