Thank you for your very accurate comments.
Accurate?
Maybe.

Personally, I would use the term "insightful" instead, but I'm not inclined to quibble over your choice of terms.
Sadly, I've said similar things to most of those you've responded to and they are certain their "one observation" - which ignores the rest of the whole - means you and I are wrong. It is disappointing but the truth can't change their minds.
Exporting (sustainable) life support to anywhere off-world is something that hasn't been done (successfully) yet.
Mainly because we haven't "needed" to ... YET.
Yes, there is limited recycling of life support on board the ISS (mainly waste water) ... but the ISS still needs regular resupply runs from surface to orbit, just to keep the life support operational. Also, a rather LARGE proportion of what gets dispatched from the ISS on return to atmosphere runs is "trash" ... which can include all the waste products that result from life support operations (which I will not elaborate on further).
Point being, the ISS life support system is for the purposes of our discussion an "open" system, rather than a closed (and therefore, self-sustaining) loop. It has more in common with the Cr2000 per 2 weeks per person life support overhead expenses that we are commonly acquainted with in Traveller.
Before we can export a closed loop (regenerative) life support system to Mars ... we're going to need to perfect an operational one on Terra, or in orbit of Terra, or on Luna. You REALLY don't want to export a closed loop life support system to Mars that ... doesn't work ... with no backup options in the event of failure. Let's just say that the "failure modes" would ... not be pretty ... for anyone dependent upon such systems for life support in a natively hostile environment (such as Mars or Luna).
To repeat what I've said before ... given sufficient Time, Tools and Tech Manuals™ ... this can BECOME a "solved problem" ... but there's a
LONG way to go in order to get there from here. Previous attempts at closed loop regenerative biome life support have been ...
less than successful. This is a REALLY HARD PROBLEM to solve. I'm sure it will be solved eventually (because it has to in order to sustain populations off world), but there is going to have to be a LOT more R&D plowed into the topic than there has been in order to get there.
The question about the pocket nuclear reactors, the net question is, per kg of mass, which is going to bring more power to the colony, an appropriate size nuclear reactor, or acres of solar arrays (plus all of the other upkeep, batteries, and such that needs to be considered).
The thing is, *IF* you can "build a machine that builds the machines" you need for In Situ Resource Utilization (ISRU) to produce solar panel arrays on Mars, you just need to "send enough stuff" to kick start the cycle of buildout ... rather than needing to send EVERYTHING. Perovskite solar cells could be a potential Tech Tree™ vector for doing this, but as with everything else you need to "perfect" the engineering (and automate the fabrication for it) here on the homeworld (Terra) first before you can export it to other worlds.
The advantage of an ISRU solution is that once you set up the "factory" to make the stuff you need using local resources, that "factory" can potentially produce way more than you could hope to deliver across interplanetary distances. Even ISRU on Luna is being looked at as a way to reduce the "throw weight" needed to launch a viable permanently manned lunar outpost/colony presence. I believe that Blue Origin (or was it some other company?) has already demonstrated a technique and process for converting lunar regolith into solar cells, which can then be used to build out the necessary power infrastructure of a (more) permanent lunar base facility. That way, you only need to "send the machine that makes the machines" (in this case, solar cells and the scaffolding/hookups to make them "work") to Luna, rather than needing to manufacture tons and tons and tons of PV cell arrays on Terra and launch them to Luna.
My current understanding is that any sort of ISRU manufacture of solar power systems on Mars is going to be FAR EASIER to do than any sort of ISRU for nuclear (fission or fusion) ... at least in the early going. Granted, global dust storms are a much greater hazard on Mars than they are on Terra (or Luna, for that matter) ... but if there are Optimus Robots available on Mars, even if it requires teleoperation, those humanoid robots can be sent out onto the surface with a "dust brush" to clear away accumulations from any solar panels exposed to the planetary atmosphere (once the winds have died down to acceptable levels for robot operations).
That said, I'm completely sure that at some point, nuclear power will become "commonplace" throughout the solar system (probably fusion) once we advance to TL=9. However, even then I would still expect solar power technologies to be employed for "colonization startup" almost everywhere within 4 AU of Sol. For anywhere that is 5+ AU from Sol, expect to need nuclear power in order to "launch" a colonial startup presence at all intended for human habitation. This will necessarily mean that outer solar system colonization efforts will tend to be "more expensive" in startup cost terms ... and not just because of distance.
And irony of ironies, it may wind up being that the upper atmosphere of Venus (right pressure and temperature, comparable to Terran atmosphere) and of all places ... Titan (largest moon in the solar system) ... might be the "best" locations for establishing permanent human outpost presence in the solar system beyond Terra/Luna, due to favorable local conditions that aren't THAT awful to engineer for.
Worst thing about living (high) in the atmosphere of Venus would be the SMELL ... due to all the sulfur (and sulfuric acid) ... assuming there's no hostile life in the atmosphere of Venus that will gladly
"eat the flesh" of humans foolish enough to try to live there (many kilometers above the surface).
Worst thing about living in the atmosphere of Titan would be the COLD ... but there are solutions to that particular problem (including, don't go "outside"). At least the magnetosphere of Saturn and the atmosphere of Titan would protect against the worst of the radiation hazards (unlike Mars or Venus).