Welcome!!!
The short answers... I think most would agree...
1) Linux Lite will work the same.. and somewhat snappier on more a system with more ram.. Using LL on all these systems may lessen your administration (though install Linux is pretty simple). I use LL on several and have tried Mint but came back to LL..
2) I'm using on 2 systems 1 with 1gb and another with 8gb.. On lesser I think it helps (I'll let others chime in on the technical aspects)
3) Chromebook you may have to confirm but I think there a few small hoops to jump through to install... But LL would be fine on 16gb I would keep it to the basics.. You home directory wouldn't have much room so I would keep to the cloud (whether it be dropbox or google or
?)
4) Screensaver could most likely be added but as these are laptops of sorts me personally I favor hibernation for battery savings or a screen timeout or a sleep of sorts should also suffice
5) For the most part... and this will be a debate.. Linux won't suffer from Windows virus (unless virus is designed to) some say no need to have AV software... Others say otherwise.. Clamshell seems to popular by most on LL.. You can search the forums and see how its set up/used and favored along with may other topics. (Search from the main forum page for clamshell or antivirus)
Don't forget the help manual as your setting up your machines...
https://www.linuxliteos.com/manual/