Can classic and fluid coexist?

We need to know if classic and fluid can co-exist.  More specifically we added the fluid components to some travelers who also have other roles to approve in modules like GL and ePro, etc... I didn't want approvals for GL to be fluid so I only configured Expenses not GLJE under Enterprise components>approvals>approvals>mobile approval options.  Even with configuration the GL approval still is going to fluid for these users.  What do I have to do to have fluid approvals only for Expenses workflow and not GL or ePro?