You can use set completeopt=longest which will insert the longest common text of the matches. (:h 'completeopt')

Be sure not to have menu nor menuone in 'completeopt to disable the autocompletion menu.

You can use set completeopt=longest which will insert the longest common text of the matches. (:h 'completeopt')

Be sure not to have menu nor menuone in 'completeopt' to disable the autocompletion menu.

This way when you'll trigger autocomplete with <C-n> or <C-p> you will not have the menu open but the word will be complete with as many letters as possible.