I mainly use multiple instances of Portable Firefox each of which has different settings and a different collection of addons. (I avoid using Firefox Profiles because editing a profile and switching to a different profile can have unwanted side effects in some situations, like, e.g., being forced to restart the browser during those moments when I am not yet ready to let all my open browser instances be closed/restarted.) Multiple instances can run concurrently by using multiple different sandboxes under Sandboxie-Plus, and, each separate sandbox can be configured individually also so, different sandboxes can have different security settings and resource restrictions applied to them. So, aside from letting me run multiple different instances concurrently, Sandboxie-Plus adds on another layer of security, which is one of the main reasons why the original Sandboxie was invented, i.e., to help secure popular browsers because ~80 percent of malware infections and successful hacking attacks happen via the browser.
The contents folder of each individual sandbox can also be copied/moved/renamed/deleted individually, and, the same holds true for each different Portable Firefox folder. Portable Firefox doesn't require to be installed by using an installer, which also means that it lets me avoid having to install Firefox into a new sandbox, and, the sandbox content also is leaner that way. I use WinRAR to be able to quickly create/extract an archive of previous content from/into a sandbox, and I use Romex Software Primo Ramdisk to speed up these actions and to mitigate slowdowns that may result from Sandboxie-Plus adding more data to a sandbox whilst programs are actively running in the sandbox.
Setting a sandboxed Portable Firefox as the Default Browser in Windows also is possible, by using an easy tweak. I use the built-in Edge browser of Windows 11 only rarely. By design, Edge uses the Windows Sandbox feature that also is part of Windows. But both Edge and Windows Sandbox have too many shortcomings when compared to what I described above, and, I see no reason to switch to some other browser like Vivaldi/Brave/etc.. In fact I still don't understand what all this fuss is about. One thing I do like about Edge is the ability to automate it with Microsoft Power Automate (former
Softomotive WinAutomation) even though I haven't felt the need to use that ability, as I am always typically too busy doing other interesting, and some less interesting, stuff with my laptop.
@play2mefish
With uBlock Origin in Firefox (or in Firefox Portable), by default there is no auto play each time when I open a link in a new tab and the vast majority of ads are gone too. Allowing what I want is just a breeze, and, I often say I'm lazy, but what I really mean by that is, I'm selectively industrious. It's actually a congenital trait, one that I like to call a luxury handicap. lol