I like the options and I’ve altered the layout etc of the new UI to what I was using prior and it basically replaces 4 addons that I was using.
However, there are things that the UI customisations isn’t allowing to modify
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Size of Target cast bar. Presently the text and bar is so small I can’t read it so I’m going to have to revert to a WA for target cast bar.
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The Map text size and clock text size. I don’t presently have a workaround for this.
I’m sure I’ll find other things that can be improved but for now that’s what I have
Blizzard said there were a lot of additional changes coming to the UI so hopefully we will get more options for changing additional elements.
One problem I’ve found very annoying is that I have some bars down the right side of my screen, and when I open my bags, they get displayed over those bars.
But what really is frustrating is that if I move something in my bag that could be put on an action bar, it superimposes the bars over the bags where they overlap as I move the item, which makes sense if I were trying to put that item onto a bar. But most of the time I’m not doing that, instead I’m just moving stuff around the bags to organize the stuff. As a result, now I can’t move an item within a bag to a spot where the bar is now being displayed where the bag and bar overlap.
Before I was using Dominos as my UI addon, and the bags were displayed adjacent to the actions bars, not overlapping, so that didn’t happen.
Not sure if this is working as intended or not, but if it is the way they want it to work, it basically means I can’t have any bars located on the right side of my screen or else I’ll inadvertently be moving stuff onto those bars if I’m not careful or just not able to move stuff to the right side of my bags.
/moo 
it appears to be a bug. If you try it with the totally generic UI, the bags are adjacent to the right-side icons, as soon as you start editing anything, they suddenly go over the bars.