The 5600, 5600SXT, Clack, 2510, etc. have all had problems over the years. The 7000 has been out for over a decade, it did have a recall of one batch last year due to a potential leaking o-ring that could cause extra salt usage.
The main problem people have with it is that it is different than the 5600, the best selling and most copied valve on the market for the past 30 years. The 7000 has massive flow rate and application advantages over the 5600 and many other valves. That being said, the 5600 series is excellent for most small to medium residential applications. I prefer the 7000 and have one of the original pre-release prototypes in my house. It has been updated from the original SE to the SXT, and recently with the XTR and now the NXT board.
Honestly, you will be fine with either one. Both are excellent valves. For commercial applications, most of the major companies use the 7000 for their single tank softener applications for a multitude of reasons.
RO recommendations, sadly, most companies claim made in USA, most are made in China. I will be doing a video review on "MADE IN USA" RO systems next month. We will be buying several units and tearing them down to show that many of these units don't include a single made in USA part and they are assembled in Taiwan or China. This is a major problem in this industry and has gone unchecked for too long.
Wait a few weeks for this to happen, you may be surprised.
RO water is technically not acidic, it may have the pH reduced from where it started, this does not always equate to acidic. And acidic... is 6.9 really an issue? Beer, OJ, Gatorade, etc are all far more acidic than RO water. Again, the massive amount of misinformation that is available online by companies trying to sell their "unique" garbage is staggering. A cheap and simple calcium filter will typically neutralize the RO water if it is acidic, but this is not a real concern. In my opinion, a very small calcite filter makes the water taste a little better, but that is my personal opinion. My wife prefers the non remin water.
Corrosive to plumbing... again, very poorly explained by most companies who are pushing alternatives or by those who don't understand basic water principals. And... the small RO system runs through poly tubing, not the whole house. A whole house RO can be needed on a rare occasion, but it is usually installed in people houses who read online about how great RO water is... lol.