I do not recommend having anything installed on your computer to monitor for Malware and that includes MalwareBytes. It is actually a great program and the free version is very successful in removing Malware. Anytime you have a piece of software that runs constantly on startup, it is going to have an effect on your performance. I am also not a fan of Browser Extensions on Safari.
You will find that the majority of Malware you may get on your Mac is actually Adware or a browser redirect that is very noticeable and using the free version of MalwareBytes will remove it. After the malware has been removed, you can delete MalwareBytes and if you need it, just download it again so you get the most recent free version.
You are correct that you should not use any AntiVirus software. There is no need to use AntiVirus on your Mac like was always the case for Windows. The 2 Operating Systems are very different and Windows is actually moving in the direction that MacOS has used by sealing the OS on a Read Only partition of your drive and using SIP (System Integrity Protection) to prevent any alteration of these files that viruses used to infect in the past. Here is a very good article by John Galt that covers just about any threat you may experience along with recommendations.
Effective defenses against malware and ot… - Apple Community
