1P_Timothy Good news, I think the cause has been found - on the 1P7 Autofill settings page, the "Always show Autofill suggestions below fields" toggle is greyed out (regardless of whether the option switch is on or off) if the "Autofill" toggle is toggled off. I had assumed that if Autofill is off, the other options would play no part.
So with all 1P7 autofill settings deactivated, and 1P8 autofill activated, I can now confirm I get login suggestions above the keyboard on most sites and applications. The doubling up of entry suggestions above the keyboard and, above the entry field is now also resolved. This is the case regardless of using either chrome, Samsung internet browser or Samsung internet browser beta. It also works with both Gboard and Samsung soft keyboards.
Finally, I tried the same settings with my tablet (which I alternate between using onscreen keyboards and an attached physical keyboard). If the browser is launched with a physical keyboard, password suggestions appear above the entry field, however if I switch to the soft keyboard at that point, the suggestions continue to appear above the entry fields and NOT in the keyboard strip. If you then restart the the browser without the physical keyboard attached, the suggestions appear above the keyboard strip as designed. However, you will have to restart the browser if you switch to a physical keyboard.
Thanks for all the help, it's focus on customer support like this that keeps me a loyal 1Password user.
Darren