Plug in SEO Free does not modify your code in any way so will not conflict with other apps.
Plug in SEO Plus aims to be compatible with all of your favourite apps apart from some other SEO apps.
If the other SEO app controls your page titles and meta descriptions it is better to choose just one app to do this.
Plug in SEO Plus is a complete SEO solution offering page title, meta description templating, JSON-LD structured data, broken link fixing, keywords and more. You don't need a different app for these things.
We're happy to look over a list of your apps and let you know of any potential conflicts. Send a screenshot to firstname.lastname@example.org.