There are a thousand different strings you could use for your resonator. Everything from cryogenically treated strings to strings shot into space to strings blessed by a shaman in a rainforest in South America.
Unfortunately this variety of options leads to a lot of confusion, a lot of misinterpreted information and a lot of misplaced convictions.
My strings containing asteroid flecks really do increase the sustain.
The flamingo feathers give me more bottom end.
The hemp makes the treble sparkle.
People, just stop. Let’s talk about the things that matter.
I don’t know all the science words but what I do know is that sound is a byproduct of things (mass) moving. Vibration. The more mass that is vibrating the more sound you get. More sound=more better. All those highs/lows/midrangey tones well you just get more of them and that is always a good thing when it comes to acoustic guitars and in particular resonator guitars. I kept that mind when it came to designing how a Mule works which is pretty against the grain when read about traditional thought concerning resonator guitar construction. Something that will help you with your Mule or with any guitar is using big ol thick strings.
My favorite sounds come from a 56 gauge set with a 18 and 16 on top, tuned down half a step in standard, and tuned to a normal open D. If you do to tune down a half step put a 15 and 17 on top. If you do a lot of bending use a 14/15. You’ll have to buy these in single string sets but this is the most bang for the buck you can put in your guitar.
I don’t play these guitars in a band, most likely neither do you. Don’t show up and tell fiddle player you’re playing in Eb. He will be angry with you. But when playing solo tuning down a half step allows me to use heavier gauge strings, which equals more mass which equals more tone.
Remember, and this is important, that your strings are the primary tone producers of your resonator guitar. Why? Because like we said before sound is a byproduct of vibrating mass. What does the most vibrating in your guitar? The strings. The more mass you get can get moving there, the better.
Phosphor bronze strings are what I put on the Mules stock. 80/20 strings are too bright. And if you are looking for some real thick sound use DR Rares. I love them on normal acoustic guitars too. They sound more worn in out of the bag.
Sure, there are tons of options out there. Spend $100 bucks and try all the craziest sets of strings you can. Do it in a a single month so you can more compare them better. Decide, buy a bulk set of them and be done with it. The tone is in your pick/finger attack, your tuning, and your string gauge. The other minutiae matter minutely. You have better things to do.