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+1 on making sure to connect battery first. It appears to be a 12/24v pwm controller, and may think 24v based on pv input. It supposedly has protection for high pv input (current specs), so connecting the high voltage panel may not have let the magic smoke out.1
Going a little over 200v on a classic200 is okay. From 200 to 248v it stops charging, but lives on to charge when the voltage drops without letting the magic smoke out.
As others mentioned, the classic won't normally draw more than rated even with more panel. To a point, extra panel is a good thing for lightly overcast days. Like pretty much any electronics though, running it at full rated output for long periods can make them hot internally and shorten lifespan.1
You may well have toasted the batteries. AGMs are quite sensitive to overcharging, and the smell is a bad sign. I would check the resting voltage on each of the batteries. If it's about normal (12.6ish volts). I would try a load test by connecting a known load of about 5-6a @12vdc (eg. auto light bulb).
BTW, shutting off half the combiner box likely wouldn't reduce the voltage. Panels are typically wired in series strings, then combined in parallel in the box. In parallel, current adds but voltage stays the same, so shutting off half the breakers would give you half the amps but about the same voltage. Some (but not all) charge controllers will auto-detect battery voltage providing they are powered up by battery first, and only connected to solar panels after booting up.
As for batteries freezing, a fully charged battery won't freeze until much lower temps than you'd get. In order to freeze, they'd have to be sitting in a partly charged state for some time. That, in itself, would lead to early death for the bank.1
In figuring out how much panel you need/want, although we use some rules of thumb, it really comes down to personal preference. There's nothing "wrong" with using 400w of pv on a 450ah@24v bank. You could bulk charge with a generator every morning, and let the panels finish charging if the weather's nice. Depending on location, you may end up doing that in winter anyway.1
That article really doesn't say much at all. 10% might be about right if I bought panels etc at a box store vs getting something installed, but it's really apples and oranges. I saw $3/watt on sale at Canadian Tire recently.1