I've sent Renogy a message asking for clarity on isolating switches.
Feed back on their website suggests they seem to be in all sorts of diabolical strife. Some due to product quality, some due to lack of service which I got the impression is a Covid virus related thing.
I try not to let bad product reviews worry me too much unless there are a lot of them. A firm may sell thousands of units, but everyone who gets a good one probably doesn't post on the internet.
Their dud unit rate might only be one per thousand, 0.1%, and that will get plastered all over the net, but you aren't going to hear about the 99.9% that are fine.
MPPT controllers are of best use in fairly special circumstances, of which I have some.
If you are desperate for power, a MPPT controller can eke out a little more in the reduced light conditions at the start and end of the day. But it depends on the power curve of your panel.
If you have a panel that is the right voltage for a 12V system, you'll be hard-pressed to notice.
Or, you could have what I have.
I have a brand new 250W panel that was left over when my son's boss changed brands at their solar installation business.
House mounted grid connect solar is huge over here. You can put up to 10 Kw of solar on your roof and get a subsidy for doing so. (Saves building more power stations as the population grows.) Thanks to Tesla and others, now we can also have batteries to use the power generated at night, too.
The boss changed brands and gave the last 4 old panels to his workers.
But - its a house panel. The 250 watts is achieved with about 31V at 8 amps.
I could use a PWM controller, but I'd only get the 8 amps - about 112 watts at 14 volts on the battery.
This is where MPPT is supposed to shine. It is supposed to take the 250 watts at about 31V 8 amps, and turn it into about 224 watts at about 14 V 16 amps.
(Nothing's 100% efficient)
I looked at the myriads of youtube videos of the cheap Ebay MPPT and many were tested, and pulled apart, and proved to be mis-labelled switching regulators, not MPPT at all.
So despite my earlier statement re: not believing everything you see on the net. I looked elsewhere.
Will this work?
I'll let you know.