Hard to quantify this perfectly, but the texture will be similar to MT3 Dye-sub sets, if that is a worthwhile comparison. They are not smooth, there is certainly some texture (though not a ton).
The Mini Base kit is intended to cover a range of ortholinear as well as 40/50% boards. Compatibility will depend on the specific board in question.
If I'm understanding the last part of your question correctly, the Mini Base kit will not work on a standard 60/TKL/100% layout board. Most of the larger keys (2u Backspace, 2.25u Enter, 2.75u Shift) are missing from the Mini Base kit.