Apple will release a new version of Mac OS 10.15 “Catalina” that will only run 64-bit software. The current Mac OS 10.14 (Mojave) will be the last version capable of running 32-bit applications.
Before you upgrade to Catalina I recommend to first verify what app’s will stop working after you install Catalina. Rolling back to the previous installed version of the Mac OS will be a very hard and costly to reverse.
The easiest way to verify the compatibly of your current setup is to install the free Go64 app from St. Clair Software. The app Go64 identifies the apps on your Mac that are still 32-bit so you can plan to update or replace them in the near future.
To completely remove redundant software from your Mac I recommend CleanMyMac. This is a great application to easily uninstall any software you want to remove from your Mac including all the hidden files that clutter our system. It is also an excellent maintenance tool that will help your Mac running smooth including general malware removal.