Advice on best way to install High Sierra please...

[Dreambird]

So... the good news is that I've managed to install High Sierra booted to the clone I have created by SuperDuper... all went well!!!  Including installing the OS and updates to Safari and 2 security updates. The drive I used for the clone is a portable 2TB flash drive (Seagate). I just assumed since it is a flash drive that the conversion to the new file system APFS would happen but upon checking Disk Utility it states that it is a "USB External Physical Volume . Mac OS Extended (Journaled)."

Perhaps because of this it didn't change the file system? The internal drive on my MBP is a "SATA Internal Physical Volume . Mac OS Extended (Journaled)" and is also flash or as they call it "SSD." Personally I have no problem with leaving it as is but I thought I'd let the change to APFS happen. If I was to do the whole thing all over from the start on my MBP I image it would "unless" I used the Terminal command

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO

available here: https://osxdaily.com/2017/10/17/how-skip-apfs-macos-high-sierra/
My main concern is whether my Time Machine would work as usual especially if I needed to restore from it as it is not a flash drive so would not convert.

So what I'm wondering right now is that it would seem High Sierra is working very well on my external clone so would it be possible to wipe my internal drive and clone it over with SuperDuper or should I go through the whole procedure again on my MBP's internal drive? That drive choked on the last security update for El Capitan with a Kernel Panic even upon several restarts. I finally had to boot into recovery mode and restore from Time Machine, hence why I decided to try the whole works booted to an external drive first now.

Also theoretically after I use iTunes 12.8.2 to install iPad OS15.1 on my iPad I should be able to easily revert to iTunes 12.6.5 if I wish to continue to use syncing for Apps capability. But if I decide to try that I'd try it from the clone first.

I'll include an explanation of why I could NOT get a download of High Sierra until recently... it was all pretty much due to that uninstalled security update quoted from a TextEdit file:

I finally did manage to download a whole 5.24GB installer of HS... AFTER I placed a phone call to Apple Support. It turns out all I needed to do was install an update to El Capitan called Security Update 2018-004 10.11. There was also an iTunes Device Support Update. Also once I updated my iTunes from 12.6.4 to iTunes 12.8.2 it showed the update for my iPad to OS 15.1 available. I did all that on a SuperDuper clone I booted from so as not to mess up my MBP because I had tried that Security update on my MBP a couple of years back and it caused a snafu so bad I had to boot into recovery mode and restore from Time Machine. It had caused a Kernel Panic that essentially locked me out of my MBP until I did the TM restore. I did that update and the iTunes updates on my clone and all went well but have not had the nerve to try it again on the MBP just yet. Apple Support was at a loss to explain what caused the fatal Kernal Panic... they just suggested to try running the update again and call them if I had trouble. While booted to my clone everything went well and then all updates installed and done Safari downloaded a 5.24GB High Sierra installer.

Only other bit of nastiness is Firefox... I had really hoped that being able to upgrade to v94.0.1 it STILL will not sign into my online banking and various other sites. Safari however continues to work perfectly! I've gotten all my bookmarks imported to Safari and am considering trying Chrome as well. Firefox has generally worked well for me however this latest "stunt" and lack of uncomplicated fixes has about driven me crazy... a shame since I've always been a Mozilla fan... maybe if I can remember how to create a new profile and what to copy over from the old one I'll see if that works. If not then I guess me and Firefox will part ways. 

Any suggestions as to the best way to get High Sierra over to my MBP's internal drive would be most greatfully appreciated. If by chance someone else with Firefox has run into the same issues as mine and managed to fix it that would be awesome as well. 
Sorry for the long post! 

[Dreambird]

Just ended up copying HS over to MBP's internal drive and so far it seems to be running fine. According to System Information it is using Journaled HFS+ file system. It just did so, I didn't do anything to stop conversion to APFS so I can only assume it didn't convert because it was installed and set up on an external clone portable Seagate flash drive.

If anyone happens to have found a solution to why Firefox will NOT sign into my online banking and a few other sites I'd love to hear about it!  All I can tell from searching Google is that there are lots of complaints but not a lot of consistent answers. I did try a reset of Firefox as was one suggestion but no joy.

[Dreambird]

Just in case anyone is interested there is a way to convert to APFS if it didn't happen when High Sierra was installed:
https://www.macobserver.com/tips/how-to/upgrade-mac-apfs-after-high-sierra/

... has to be done in recovery mode.

Found out why mine stay HFS+... it's because I used a bootable clone to do ALL my upgrading being leery of the mess I had on my hands over a simple security update before on my MBP... if you do that and when you're satisfied that it went well you clone it all back over to the internal drive it will not convert to APFS. There is of course the Terminal command I mentioned as well however with that method you are on your internal drive with all the attendant risks.