You should not expect that doubling up on Anti-Virus software will offer double the protection. You should not consider that one piece of software offers protection against this or that, and this other one offers protection on the missing component not offered by the first one. 


You can be certain, that they actually cancel one another out, shut off each others features, and in some cases, entirely block particular features and components from even being downloaded to begin with. 


If you are changing your software, you’ll need to shut the existing one down before moving forward on the install of the new selected software. You’ll need to 100% remove the existing software, and if you have any doubt at all that every file and folder has been removed, or if you are not sure how to be sure, you should not be the one performing this task. 


Happy computing.