You are completely right! I don't know why I overlooked this.

I assume if I plug it in (whether cigarette or AC adapter), there's no way that (while actively driving) that I would be draining the car battery more than charging it, right?

Yep that's correct

It's possible to outrun the alternator, but it's really unlikely in these vehicles. The alternator is IIRC 140 amps. (So about 1600 watts - if you consider that compared to 100w solar panel, you can see that the alternator has a lot more energy output). A fridge as an example typically draws a peak of 7 amps, but normally they draw around 1.5 amps. So the draw is pretty small.

If you add a bunch of electronics and auxiliary lighting and ?? maybe you can exceed the alternator capacity. A 100 watt solar panel probably won't do a whole lot if you're drawing more than 1600 watts already.

Why not use something like this?

Toyota 4Runner | VSS System™ | 90 Watt Hood Solar Panel - Cascadia 4x4

i like this. it's a wasted space and why not use it, right?

solar panel efficiency decreases when it gets hotter, so an elevated panel that can flow air under it will be the most efficient

(also, in regards to cost per watt that is almost 5 times more expensive than a regular solar panel!)

For the use case the OP describes, I would recommend the following:

(1) Mount on the roof rack (leave it there for the trip), wire down the A-Pillar windshield channel to the charger in the engine bay [single or dual battery setup]

(2) Transport panels inside the car (set up on ground / lay on windshield / lean up on tire / etc - flexible placement when on the campsite), wire-up a plug quick connect up front somewhere, charger in the engine bay [single or dual battery setup]

(3) Go with a Goal Zero type system - separate battery and panels - deploy flexibly.

The only thing I see that's needed to run into the cabin would be power - e.g. dedicated higher load always-on 12V for a fridge.

I'm currently using the #2 approach.

You can also go in through the back hatch without drilling

How can I remove the fin?

How to remove 2010-current 5th Gen 4runner sharkfin(XM radio) antenna - YouTube

Portable battery, portable solar panel. I’ve been considering getting this Jackery Solar Saga 100W panel. I already have the 500W Power Station battery.
100W Solar Panel, Foldable with USB & DC ports

– Jackery

Attached Images

   

Just keep in mind that's about double the price of a regular panel, so if you don't need those features (carry handle, USB charger, etc) you can get a panel for a lot less money

True. But I’m willing to pay more for convenience, and foldable for easy stowing in the cargo area. A lot of regular solar panels are large and have sharp corners.