I'm working on creating a table with eForm in Drupal 8.
Since label and textfield(input) stick together, can I insert label and textfield(input) into separate
The Render API, similar in Drupal 7, allows you to add a #theme property to use a hook_theme defined template. The theme definition should use "render element", and that will be available in the template preprocess function. The way that it's usually done is to modify or create the render array in the preprocess function, and set #theme to table (in Drupal 7 calling theme('table') was possible).
Edit: Removed second paragraph which referred to modifying the theme.