Short answer is that if you don't have an MFT/3 then the stand could double as a work surface when the Kapex isn't being used. Caution !!! If you don't have an MFT/3 and you get the MFT mini then you will end up buying the MFT/3 shortly thereafter.
Long answer
If your Kapex is going to stay in the shop and not have to be moved:
You can build a table or bench for it to sit on at any height you want. There are a lot of great ideas and plans on this site as well as people that are willing to help you if needed. This is the least expensive and best option.
If you need some portability:
The MFT mini or the UG cart are both excellent options since the height of the Kapex cutting surface is the same height as the MFT/3 when using either option. Right now there's only $63 difference. I'd go with the UG cart if I had an MFT/3 because the cart is easier to move around. I'd go with the MFT mini if I didn't have an MFT/3 because then it could double as a work surface when you aren't using the Kapex. That would help someone find out how valuable an MFT can be. First time I looked at an MFT/3 I thought it was too small and too wobbly to be of any use to me. I finally ended up getting one and now I'm buying my second one.
If you need to take your Kapex out of the shop:
This is what I need. I bought a Kapex last year and sold my Ridgid miter saw and stand. In a couple of months I'm going to have another house to remodel so I'm at the point of having to buy a stand for my Kapex. This time I want a stand that has wings so that the material I'm cutting has continuous support. I did a lot of research and have boiled it down to 2 options, the UG cart and wings or the Best Fence system from Fastcap (they have a non-Pro version that's not listed on their site). My opinion is that if you normally cut boards 5" wide or less and not longer than 8 feet or so then get the Festool option. You can do the occasional larger board but it can be more difficult. The other limitation that I see to the Kapex is that it can be unstable on rough or uneven surfaces but that can be overcome with either a shovel or a platform for it to sit on. If these limitations don't factor into your use then the cart and wings are a great option. Wish Festool sold it in the US with an imperial tape instead of metric.
I'm fairly certain that I'm going to go with the non-Pro Best Fence system for many reasons. However, if the above limitations weren't a factor for my use then I'd go with the Festool option if I bought it this month while it's on sale.
However, I would get the UG cart if I was going to use the cart in a small shop and then match it to the Festool wings or the Best Fence wings.