what is better approach for single wp project with ticket and other functionality


There is a project where single WP install in fine not required multisite for running project.
Now i am planning to integrate for Support ticket , affiliation etc.

So i am in dilemma as per followings:

1. install plugin support / affiliate to same site
2. create multisite system and project on main site
and support.mainsite.com as subsite
and affliate.mainsite.com as subsite

in multisite i will use user sync plugin etc.

So please suggest me what is better approach for user experience, maintainability,
and server load and speed .