It’s hard to quantify it exactly but you will need to be proficient on a computer. When you get to the stage of writing simulations you will spend about 1/3 of your time reading and outlining and 2/3 of the time writing. Your average simulation response could include 2-4 pages of text (if quants are not involved) for a 60-90 minute simulation. Some of that time will be spent thinking as well so keep that in mind.
I haven’t met many people who are slow typers anymore but if you are significantly below average this may be a good time to take up some activities to increase your typing speed. If you are average then you’ll be fine in my opinion. You don’t need any kind of above-average level of typing to do well on the UFE. Especially if you become a strong case writer and can get your thoughts down concisely.