This is debatable, but in my opinion you should place the filters AFTER the tank, for two reasons: 1) service on the filters will be easier in that position; and, 2) it is better to allow your pump relatively free flow into the tank, where pressurized water can then flow into the filters. That is just my opinion based on general plumbing knowledge. I haven’t installed more than a few of these systems, as we have very little call for them in the SF Bay Area (the ones I installed were in rural areas of Napa and Solano Counties).
One thing I forgot to mention in my last post is that there are some concerns about possible health hazards of in-line water filters (fiber and activated carbon). These filters can trap sediment that provides a substrate for bacterial growth in the filters. There are some filters that include sterilization capabilities, with ozone/ultraviolet light, and I would recommend using these.