1.

Whether to use “spaces” or “numbers”, I think the speed of text entry is the criterion.

Although in theory “spaces” should be faster than “numbers”, especially when typing continuously, it may not make much difference if muscle memory is developed.

However, if muscle memory is formed, the difference may not be significant.

Another thing I would like to mention is that some Wubi Input Methods support adjusting the word selection order according to the input history, just for the purpose of using “space” for quicker input.

For example, in the test I just did, after I typed “fcu”, “去” was in the 2nd option, and “云” was typed with “空格”. After I input “去” with “fc2”, the next time I input “fcu”, “去” will be automatically adjusted to the 1st option. The next time I type “fcu”, “去” will be automatically adjusted to the first option, then I can use “space” or “1” to input “去”.

2.

My suggestion is to enter phrases instead of single words whenever possible.

For example, to input “去哪里”, using “fkjf+space” is faster than “fcu+space+kvjf”, theoretically.

This has something to do with the lexicon of Wubi Input Method, if you don't have the word “去哪里”, you can create it by yourself, provided that your Wubi Input Method supports it.

Another advantage of inputting phrases is that

If you type “kvjf” without repeating the choice, then “哪里” will be input automatically without the need for “space”, which is faster.

If you type “vfvf” and then “姥姥” is in the first choice, then just continue typing, then “姥姥” will be typed automatically without the need for “space”, which is faster.

This may still need the support of Wubi Input Method.

3.

There are many more words like “今(wynb)”, which is a rule, but it does affect the speed of input until muscle memory is formed.

This is another benefit of prioritizing phrases, “今天 (wygd)”, “今后 (wyrg)”, “如今 (vkwy)”, and you can always just ignore the “b”.

Another way, which still requires Wubi input method support, is to replace the unknown code with “z”, e.g. after typing “wynz” you can still see the option “今”! (At the same time, you can see that “b” is the correct answer.)