Gaining muscle memory in your fretting hand can be a bit more challenging when you're playing different types of guitars, those being electric, acoustic, classical, 6-string and 12-string guitars. And I never met a performing guitarist that didn't have several.
When someone asks me, "Why do you have more than one guitar?" My answer is, "The same reason you have more than one pair of shoes."
I could include the bass guitar, but it's a different species and I'm assuming this thread is about standard guitars.
Within these different types of guitars, you'll find that the fret size, neck length and neck width, or "nut width" (where the strings are anchored between neck and headstock) will differ depending on make, model and type of guitar. The distance between strings will also be different for a few reasons.
The neck length, or scale length (from nut to center of 12th fret) come in three sizes; Short, Standard and Long. Short necks range from 24" to 24.75", Standard necks range from 24.75" to 25 1/2", and Long necks between 25 1/2" to 26 1/2". The difference between shortest and longest is typically 2 1/2", with the frets making up the difference by being either shorter or longer.
The width of the neck is measured at the nut. From the nut to the body of the guitar, the neck can widen 3/4" or more. Typically, electric guitars have the narrowest neck with the standard being 43 mm. An acoustic guitar can have a nut width up to 44.5 mm. Classical guitars, with the widest neck, are usually around 52 mm. 12 strings are slightly wider than a standard guitar, and their string spacing varies between make and model.
All these variants are miniscule to the eye, but to the hand they are immediately noticable. Most accomplished guitarists can feel the difference of 1 mm in the neck's width. This is one reason why at times, especially for newcomers, you'll try playing a guitar that seems more difficult or doesn't feel right.
When you're first learning chords and scales, you're using your brain's memory as you slowly fumble from one chord to another. Then, rather quickly, it's like your fingertips grow their own little brains and you don't have to think about it anymore. The same goes for breaking the habit of looking at the fretboard. With practice, in a short time your arms will do the thinking, allowing your eyes to search the audience for groupies. Just keep in mind that if you want to play different types of guitars it will take a little longer to get used to the feel of various necks and frets without looking at them.
Here's a few tips my instructor gave me that were invaluable, not just for playing blindfolded but playing better, more comfortably, and building muscle in the hand and wrist:
"There is no one correct way to hold your wrist and hand at the neck. As long as you can make all the strings hum harmonically without causing any pain (to yourself or the audience), you're doing it right."
"Adjust your strap for the guitar you play. Electrics are thin and heavy, acoustics wide and light. Keeping your strap at one length won't always work for every guitar. And looking cool like Jimmy Page with a Les Paul hanging to your knees- without opiates -will kill your back."
"Before a gig, practice your leads on an acoustic to tone your muscles. That way when you play the electric, your fingers will move like a spider across a hot-plate."
"If John Lennon had blisters on his fingers, it's because his guitar was collecting dust."
And finally, whenever you find chords or scales or anything about playing guitar difficult, don't give up. On a 6-string guitar with 24 frets, there are over 156 million possible chord patterns that can be conjured. Even professionals who have played for decades will fumble their way through new chords they're learning. There's always hurdles and you'll always get over them.
If you want the fast track, learn to play the air guitar. You'll never have to look at your fingers again, never have to tune it, they're very affordable, and no one will ever steal it.