iCloud mail sync and Imap google mail

Hi,

I use the mail app to access my gmail account with Imap.

Should I still enable iCloud mail sync ? I'm not sure since the gmail is already replicated on all my devices, if I enable it, iCloud might unnecessarily sync emails.

I notice that when I disable it, it works fine but for example I may lose some email autocomplete for contacts that are not in address book.

What's the proper way to set this up ?