Sophos AV always runs double instances of it's app. How do I just have 1 running?
Simple ... Uninstall Sophos.   Check with Sophos on how to uninstall. 

Simple put,  Apple attempts to provide all the malware detection and removal you need in Mac OS X.

"Effective defenses against malware and other threats" by John Galt
https://discussions.apple.com/docs/DOC-8841

"Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams"
https://support.apple.com/en-ca/HT204759

"MalwareBytes Anti-Malware for Mac Removes adware and malware Revives your Mac."  MalwareBytes has a more restrictive filter for adware than Apple. MalwareBytes has come to be accepted as the only malware detector you should consider.  For those pestered by browser attacks consider MalwareBytes.

https://www.malwarebytes.org/antimalware/mac/