The 17.5 fixed short tail doesn't work very well for windfoil. It's good for winging, but not windfoil (GoFoil changed all their focus to winging). The reason why the 17.5 fixed short tail doesn't work is that is has no stab angle. It's flat. The weight of our sail near the nose of our board creates a lot of downward pressure. With winging it's the opposite because the hand-wing provides lift like a kite. We need a tail that counters the downward pressure of the sail weight and the 17.5 fixed does not do that. You might get a little more lift from a 20 inch fixed to compensate, but I haven't tried it. I doubt it would be good, again, due to no stab angle. The Maliko tail that you bought is a good choice, or the flip-tips tail (although the flip-tips are hard to find).
I wish GoFoil still made the Maliko. At 190 lbs it's the perfect foil wing for you. The new board you got is plenty wide enough to initiate great turns with the Maliko. I'm 150 lbs and the Maliko still turns fantastic. Like you said, you will be using it under 20mph wind. That is perfect!
One other thought. I've done many structured tests of the speed between the Maliko and EZ1600 (slightly smaller than EZ1800), and the EZ is NOT any faster. The EZ glides better than the Maliko when the power is shut off, but it is not any faster. Just an interesting find.
Here is a video that explains the wings: https://www.youtube.com/watch?v=9Ueo7WEftus
This video also has some talk about wings: https://www.youtube.com/watch?v=diMgdmIg8hE&t=227s
At the bottom of this link are some other resources: https://www.ericthebige.net/windsurf-foiling-progress.html
This video is great to watch in slow motion for technique: https://www.youtube.com/watch?v=FeR4b7in84w
This article will help with the jibe: https://www.ericthebige.net/wind-foil-jibe---flagging-technique.html
This article for wave riding: https://www.ericthebige.net/windfoil-wave-technique.html
This helps understand the difference between windfoil and WWF: https://www.ericthebige.net/difference-between-windfoiling-and-windsurf-wave-foiling.html