Many larger municipalities are using Chloramine (Chlorine + Ammonia) to treat water these days. If your water has Chloramine, you'll need special carbon blocks to remove these chemicals. Regular carbon will remove it, but only for a short amount of time.
As for refillable DI, yes, they will work with any RO system. You simply remove the sealed cartridge(s) and the line coming from the RO membrane. Add a longer line to go to the refillable cartridge, and you're done. I love the color-changing DI as it gives a visual cue as to how much has depleted, but it's not 100% accurate. A TDS meter on the product line will often show 0 TDS even after the color has completely changed. No need in wasting good resin, so I highly recommend a TDS meter. Even if it's just a single stage meter, you need to know how clean the product water is. Just my 2c...