I'm not sure if this is what you mean, but you can turn off the password manager and then Firefox will neither ask for your Master Password nor try to fill in or save new logins. Maybe that will help? The setting is on the Options page:

"3-bar" menu button (or Tools menu) > Options

In the left column, click Security. On the right side, uncheck the box for "Remember logins for sites". When you're ready to use saved logins again, return to this page and check the box.

Another thought: Windows allows you to create separate users on your computer to keep everything distinct, such as downloads, documents, and settings for many applications, including Firefox.

I'm not sure whether Windows 10 makes it easy to switch between users, or whether you want the others to have their own Microsoft accounts, so it may be simplest to keep it all under your account. In that case, you could try creating individual Firefox profiles for different users. This keeps each person's settings, bookmarks, history, and passwords separate.

One-Time Setup

(1) If you want your session to resume automatically, change your startup setting

When switching between Firefox profiles, all your windows and tabs will be closed. If you have regular history settings -- not automatic private browsing, you allow history to be saved, you don't clear history at shutdown -- then Firefox can restore those windows and tabs when you start up again. That is set on the Options page as described here: Startup, home page, tabs, and download settings.

(2) Create the new profiles

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the Create a New Profile button, then click Next. Assign a name like Timmy and click the Finish button. (Don't use the Choose Folder button.)

Repeat for each person who needs a profile. You also could create a Guest profile in case a stranger needs to check their email or do something else that could mess up your settings.

(3) Create a bookmark for the about:profiles page in your profile

Bookmark the about:profiles page to a conspicuous location. For example, you can click and drag the little i-in-a-circle icon to the top of the bookmarks menu or the left end of the bookmarks toolbar. (To drag the icon to the bookmarks menu button on the toolbar, pause over the icon for a few seconds until the menu opens and then you can move the mouse pointer down and "drop" it past the Recently Bookmarked section.)

(4) Create a bookmark for the about:profiles page in the other profiles

Scroll down to a profile you want to open and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but I think those are still "under construction" so please ignore them.)

Firefox should exit the current session and then start up using the new profile, which will just look brand new.

Repeat the bookmarking process.

Using Profiles

If someone needs to use Firefox, and they can see they're not interrupting something critical, then can go into about:profiles, set their profile as the default, and then use the "Restart Normally" button. (If they're feeling really polite, they can switch back to yours when they're done!)

Each person can install a distinctive "theme" so that the toolbar area is personalized and immediately recognizable. The Mozilla Add-ons site hosts a large collection of them:

https://addons.mozilla.org/firefox/themes/

If you run into a problem where you do not want someone's profile to be closed when another person needs to use theirs, you can create desktop shortcuts to each profile to runs as an isolated instance of Firefox. By isolated I mean that it can run alongside the main instance of Firefox but is not treated by Windows as your default application. Any links opened from the desktop will open in the first instance of Firefox and not the isolated one. But this post is already really long, so... another time.