being a dinosaur that started with wood racquets, my swing mechanics have a foundation firmly rooted towards the flat end of the spectrum -- i'm "spin curious" to see what different strings might offer.
i have a backup frame getting strung up with shaped poly -- lynx tour, my 1st venture into the poly realm -- which may be extreme, so thinking a less radical syn-gut with more spin potential will be a nice compromise?
Dinosaur?... I'd say more like
gifted with divine insight of a bygone era.
I was a pure serve and volleyer as a kid using wood racquets on grass courts in the summertime. It was magical. I always used syn. gut (SG) in my racquets back then and I never trended away from it later on. Poly never did anything for me (other than annihilating my arm a few years ago), but multis have always underwhelmed - they're soft and arm-friendly for those who need that, but they just degrade too fast in my book.
Even though I play with 97" or 98" frames now at age 58, I'm still home-sweet-home with a semi snug bed of syn. gut. I like a 16 ga. option for a more open pattern like a 16x19, but a thinner 17 ga. seems to be better in a dense 18x20 pattern. Are they all the same? I say no.
Babolat seems to be a terrific general purpose syn. gut that's moderately soft. I've used this in 16 ga. and 17 ga. Other syn. guts that seem to also play moderately soft for me include Prince Original SG (without Duraflex), Volkl Classic SG, and probably one or two more that I'm not remembering right now (perhaps Head and Wilson SG Power).
My favorite SG these days is from Kirschbaum. It seems to be just a bit softer than the moderate SG's I mentioned above. You can go even softer with Forten Sweet, which is about as plush as some multis, at least in my book.
A couple SG's that are more firm and durable are Gosen OG Sheep Micro and Prince SG with Duraflex. These are too stiff for my taste, but they're pretty good for some folks in some racquets.
I appreciate the curiosity in terms of seeking spin. In my experience, I get more RPM's on the ball with the right racquet and not from a certain string setup. SG is firm enough to give me decent control and soft enough to allow me to slug with the high school kids I coach nearly every day when we're in season. It's affordable enough to replace whenever I want and I think its performance is great for my all-court game.
If you have to scratch that itch and sample a poly layout, I'd say stick with a hybrid (not a full bed of poly) and use a lighter gauge of poly that shouldn't be as inherently stiff as a thicker string. Locals who use me for stringing have found great success with a hybrid of Isospeed Baseline 1.20mm mains combo'ed with Gosen OGSM 16 as a cross. This layout is about as firm as a full bed of 16 ga. syn. gut. You might like this sort of hybrid, but you might also find that it simply plays a bit more dead than a full bed of either syn. gut or multi.
And if you sample a poly and then start to feel some grumpy-ness in your arm, get rid of that stuff right away. The right SG at the right tension might just give you a better balance of everything you need than any other string out there.