You’re definitely never too old to learn to play. You can learn anything you want whenever you want. It may not be what a specific age group may be looking for but that’s a different issue. Learning is lifelong!
As for the overwhelming info you’ll find online; just pick and choose what you want because that will make you YOU.
Even though you don’t understand everything people are saying, it’s important to simply be exposed to the discussions themselves and eventually things will fall into place or may trigger a question or even an answer.
A basic understanding of music theory/guitar basics goes a long way of course so definitely keep digging or go for structured lessons but don’t worry too too much.
I don’t believe anchoring your arm while strumming (or picking) is a good idea unless it serves a particular (and temporary) purpose such as palm muting, specific types of picking, or even just to rest your arm (or hold the guitar for some reason or movement).
You need to remain as free as possible to have agility in your playing. Anchoring for any other purpose will probably tire you out if not cause repetitive strain injury altogether.
Don’t forget that a lot of muting also happens in the other hand as well as sometimes you need to control the sound while also strumming in a less restrictive way such as the intro to ‘Long train runnin’ by the Doobie Brothers.
Music theory is definitely not for everyone as some people who are simply collectors or ‘listeners’ (and self-proclaimed virtuosos of course 🙄) would not make any use of it. For those of us who create or reproduce music however, especially those who require interaction with other musicians, sheet music, and some software, having a basic understanding of music theory and music terminology is essential.
I remember one particular time back in college when I asked my jazz guitar teacher what to improvise with over a specific chord progression … his answer : “play anything” and smiled. Needless to say, I ended up hating him for a while 😂 but it was only later that I understood that he meant ‘play/use anything from your toolbox that YOU think will fit because your interpretation will be unique and will bring out the artist in you’.
This advice turned out to be true however it did require me to ‘keep adding knowledge and technique’ to my musical toolbox. Therefore, every time I learned something new, I now had an extra item that I could use when writing, composing, or improvising.
“You don’t know what you don’t know!” 🤷🏻♂️
I wish he had explained that to me better because for some reason that lightbulb didn’t light up for me at that moment. 30+ years later however, my toolbox is now a shed and I need to add an extension to it! 😆
I did learn however that there are many people who will attempt to make you feel like you don’t have that ‘special quality’ to be an artist/musician however today I know that this is really only their attempt to hold you back from making more progress than them. Sadly, there is lots of competition out there and considering that there is plenty of room for artists out there, there’s no reason for this to occur.
I’ve even had an old college ’friend’ withhold sharing his ‘guitar secrets’ because he said they were ‘his’ secrets. Needless to say, his music is still a “secret” today and he became an accountant (not that there’s anything wrong with that) but he could have at least influenced someone instead of turning out to be the selfish person he chose to be! 🤷🏻♂️
Facebook is full of music theory groups therefore there are plenty of likeminded musicians who are willing to exchange knowledge with you out there. I don’t recall however ever seeing a group about ‘guitar music feelers’ (nor will I check)!
