If you're asking whether there's a way to eliminate n words and drop into insert mode to conveniently replace them with something else, yes there is, with a few variations.
With your cursor on the
a, you could do
2cw) to remove
a testing and drop into insert mode with your cursor before the space preceding
line. This operation can also span multiple lines, so if you had your cursor on the
this is a testing line
and this is another one
5cw it would join the lines and drop you into insert mode with your cursor placed between
this is is another one
w movement in this context encompasses characters from the cursor to the end of a word, so if you start from within a word, the beginning of the word will be unaffected. For example, with the cursor on the
flexible stuff bends
xible stuff and puts you insert mode with the cursor after the
fle bends. You could also have used
e instead of
w in all the previous examples and it would behave the same.
If you wanted to operate on the entire word instead, you could use
ciw. In the previous example, typing
flexible stuff (including the following space) and puts you in insert mode with your cursor right before
ciw acts a bit differently, and it's easier to try it out and get a sense for it than for me to try to describe it.