Good call on getting an RO based system. We have around 400 tds here and you can chew through a DI tank in less than a day on some jobs.
IPC Eagle has made the XERO system for us for the past 6 years. If you mainly do residential you cant go wrong with it. - https://shopwindowcleaningresource.com/xero-pure.html
Check this link out it gives a full breakdown on all the features. - https://windowcleaner.com/xero-pure/
The next step up is the full IPC line - https://shopwindowcleaningresource.com/pure-water-systems/ipc-eagle.html ) Look at the Hydrocart.
The XERO or the IPC Hydrocart will handle your 400 tds just the same. With the Hydrocart however you can have a built in pump, battery, electric or gas. You can also get them with a really nice hose reel built right in.
The Hydrocart for running 2+ poles on a jobsite. Better suited to commercial work.
The XERO Pure is smaller, lighter and more nimble.
We sell a lot of Hydrocarts but the XEROs move 30 to 1 because of the price.
Let us know if we can help 862-266-0677