Huzzah! After 6 months of wondering, I finally have an answer!
Ahem.
You are spot-on in pointing out archetypal thinking. After re-reading the descriptions of both types I can definitely see how they could work together, but I'm still curious about certain aspects that look like they would clash spectacularly. To use myself as an example: 7s have "extroverted energy" which is felt by everyone around me when I socialize, yet I am an introvert. INFPs prefer to focus on one "mission" or goal in life, yet my attention and interests are so scattered and varied that by my mid-twenties I still haven't figured out what direction to go in. INFPs are feelers (obviously), yet 7 is in the "thinking" center. And so on.
Those are the kinds of things I'm wondering about: how do the supposedly "opposite" qualities of the archetypal ISTJ and 7 resolve themselves in your particular personality? Since you asked for specifics, here's a list of such opposites to get you started:
- ISTJs are often described as very dutiful, while 7s are often described as free spirits.
- 7s are thought to be undisciplined, while ISTJs are seen as the perfect models of discipline.
- 7s generally prefer freedom over security, while ISTJs are often willing to sacrifice their freedom to maintain security.
- ISTJs are stereotyped as "responsible adults" while 7s are stereotyped as "kids bouncing off the walls of a candy store on a sugar buzz"
Feel free to add and discuss any other discrepancies or opposite traits you can think of. And thanks for the necro! I had just about lost hope that I would ever find an answer.
Ahhh hahhaha good god I never thought I'd see that dancing banana gif ever again
I'll try to work out things on a case by case basis. Sorry about the formatting, quite frankly this interface isn't the most intuitive. Also, I should add that I'm still trying to figure out what my functional preferences are. I just kinda went with ISTJ because my functional stacks seem to fit the best here.
To use myself as an example: 7s have "extroverted energy" which is felt by everyone around me when I socialize, yet I am an introvert.
First and foremost, I think in order to socialise there has to be some kinda bonding process. I'm extremely introverted out of habit by now, but when I was younger I had this. extroverted streak going on. Trying new things, etc etc.
. INFPs prefer to focus on one "mission" or goal in life, yet my attention and interests are so scattered and varied that by my mid-twenties I still haven't figured out what direction to go in. INFPs are feelers (obviously), yet 7 is in the "thinking" center. And so on.
...I'm a bit iffy about type descriptions. They make INFPs sound like unicorns or something. Also, that aux Ne should probably manifest itself in seeing multiple possibiliities. That's just my take on that, though.
Alright, to the questions.
Those are the kinds of things I'm wondering about: how do the supposedly "opposite" qualities of the archetypal ISTJ and 7 resolve themselves in your particular personality?
They don't.

If there's one thing I've come to conclude, it's that people, me included, are complicated creatures.
- ISTJs are often described as very dutiful, while 7s are often described as free spirits.
I'm a dutiful free spirit.
Well, to be more specific in a way that language requires me to...
I like having autonomy. I'm also very loyal towards people who are loyal towards me. I don't like being dutiful out of a sense of obligation. An example would be the case of family: I am loyal to family, because they have consistently been there for me, even though their treatment of me at times is also abyssmal.
On a more practical level, is there anybody whose happiness is not intrinsically tied to their relations with others, even as relation of production in the commonwealth of societies or whatever the stuff there is? The way I see it, I am free, but bound to all of these things. I reject them out of impulse, but also, stay bound because there's literally no other way.
- 7s are thought to be undisciplined, while ISTJs are seen as the perfect models of discipline.
I'm not a model of discipline in any sense of the word other than self-discipline. I have high ethical standards to the point of paralysis. (I guess in Enneagram terms it probably sounds like disintegration. Which it probably is.)
- 7s generally prefer freedom over security, while ISTJs are often willing to sacrifice their freedom to maintain security.
Yes, and it's a constant tug-of-war. But, the way I see it, the core desire of 7 is to not be in deprivation., and they achieve it via planning. It's a very ISTJ thing to do, if you boil it down to that sense.
On a more individual level, it's really more like there's two different impulses that I constantly have to choose between. I often make the wrong choices when I sacrifice my security for freedom, but at the same time staying in the same spot, in "security", would just cause me continued misery.
If there is a choice to stay in the same spot where I have a reasonable amount of autonomy, freedom, access to personal pleasures, etc etc, I'd probably do it. And I wouldn't give it up. ever. But it's not a choice like that. It's always a choice between a rock and a hard place.
- ISTJs are stereotyped as "responsible adults" while 7s are stereotyped as "kids bouncing off the walls of a candy store on a sugar buzz"
Both stereotypes seem false on an empirical level. There is nobody who is one dimensional. xD
...But
... I'm often very reserved. At the same time, I have the impulse to try some new things, just for variety. There are times when if you asked me what I was doing, I won't have any answer. I'll just suck it up and take the responsibility.