First, MalwareBytes and any “system maintenance utility” like Fortnet are no comparable. MalwareBytes is anti-malware, and is not intended to reveal overall system issues.
I have NO experience with FortNet. It appears it is one of countless utilities like it.
As an alternative, I can easily recommend CCleaner. I’ve used that for MANY years on now hundreds of PCs, and it not once has been the cause of problems. The “free” version can remain installed and be used periodically. I have the paid version (SO long ago I grandfathered in to a lifetime license!). The paid version can be set to automate many CCleaner tasks. You almost certainly do not NEED the paid version unless you desire that functionality.
Skimming Fortnet it appears an initial install is a 24-hour trial, after which you should pay or uninstall. If I’m reading it right, it’s pretty useless after 24 hours. By comparison, CCleaner (presently and still) has a true “free” version and is not time-limited in its functionality.
Having said all that, I suggest a few settings in CCleaner I always make when leaving a free version installed. Also, I do not ever use the Driver Updater! I rarely use the Software Updater. YYMV.
For other people’s systems that aren’t tech savvy, I deselect every option in customize during the install. Once installed, in CCleaner settings, a few options:
Smart Cleaning: all off
Updates: your choice, but I suggest deselecting automatic updates for free version users. No need to have it constantly pestering.
Advanced options: select the two options to delete only after 24-hours (one is on by default).
Even in the paid version I use the Performance Optimizer as a suggestion list only. I’m a MS certified engineer so prefer to handle such issues manually. It’s quite handy that CCleaner tattles on such heavy-hitting apps though.
I ALWAYS configure Custom Clean, some highlights are for all browsers cleaning cache, “index files”, and “temp” files. Go ahead and clear download history Etc. if you want - I sometimes find that handy to leave intact.
I deselect emptying the Recycle Bin (I rarely use it, but IF I did want to I want to be able to ! If free space is that desperate it’s time for a bigger drive. I also enable temp files, clipboard, memory dumps, chkdsk files, WER, Wndows delivery optimization, and web cache.
Apps under Custom Clean you’re on your own - the list largely depends on what you have installed.