1, 3, and 4 - Step 2 can only be done after step 3 - But I’m sure you knew what you meant. 
OPTION 2:1. Stay as I am and whenever I perform a zypper dup, I’ll have to reinstall the drivers manually from nvidia like I did now.
You don’t need to reinstall the drivers after every zypper dup, it’s only required if there is a kernel update.
OPTION 3:1. I could install the opensource drivers (modesetting or nouveau). When I was running leap, this nouveau driver was giving me hell. Sometimes my graphics was terrible and then during system boot I would get some errors and had to reinstall the OS. I am concerned about using the nouveau drivers.
OK - If you have good reason to not use the nouveau driver that’s fine. You might want to give the modesetting option a try, @mrmazda has now kindly provided the link to his article.
What do you mean by ‘it’s important to not use the (KDE) update applet with Tumbleweed, I would remove it completely (“plasma5-pk-updates”), only use “zypper dup”.’ What is the KDE update applet?
The KDE update applet (“plasma5-pk-updates”) is an automatic updater. It’s that which is issuing the pop-ups shown in your first post. It works OK with Leap and is a convenient method of keeping a system up to date. Tumbleweed however is different in as much as each snapshot is, in effect, a new distribution, hence the need to use “zypper dup”.
One of the safest ways to update TW is to log out from the (KDE) desktop session, switch to a virtual terminal (Ctrl-Alt-F2), login as you normal user, then execute:
sudo zypper dup
After the update is completed, if a reboot is required then
sudo /sbin/shutdown -r now
if a reboot is not required you can exit that terminal session
exit
and switch back to the graphical session using Ctrl-Alt-F7 and login.
The primary reason for doing the zypper dup from a virtual terminal whilst logged out from KDE is just in case (very remote chance of) the desktop session crashing during the update.