First question - how does anyone measure petrol 'quality' on the road?
I've travelled those countries on a small motorbike with no problem.
And reading the HUBB, riders regularly travel them on modern sophisticated bikes and also don't report any problems.
We met riders on big newish BMWs, Triumphs, KTMs. All fine.
Yes, there can be shortages of petrol in comparison to diesel (mainly in southern Ethiopia we found, in 2000, but it constantly changes). If you ask around, and shake lots of hands (that is - everyone's), usually you'll find a black-ish market supply.
In my experience, even what appears to be poor petrol won't do damage unless your racing and torturing your engine. On a 900 Ducati in Ukraine in 1996 there was only petrol that looked like mud (literally) - for a bike that back home, owners would say 'only this or that petrol should be used' and 'only a dealer should work on your engine'.
But again no problems and the bike went on to do UK-Turkey, UK-Portugal etc.
If you're worried about octane, treat your engine gently, don't let it labour and it should be OK. Listen out for 'pinking' or 'knocking' or 'detonation' (depending on what it's called in your country) and ease the throttle and change down a gear if you hear it.
If you have a catalyser (you don't mention) then you'll need unleaded everywhere. Can't comment on that but I seem to remember that it's pretty universal.
Maybe take injector cleaner if you have fuel injectors.
As far as Ethanol is concerned - well, what a can of worms!
Here's my understanding:
There's ethanol in UK petrol now (maybe 10%?) a lot more in US petrol. Whether you should be worried about it depends on the age of your vehicle and how many years you'll stay in any of those countries you mention. If just passing through, I don't think it'll be any problem. It's long-term use of ethanol that can be detrimental. And also depends on the age of your vehicle.
I've done a lot of research on this.
My 1999 Aprilia RSV1000 has been idle for 3 - 4 years. Last month I set off to an MOT station for its annual test - the first for 4 years.
Stopped for petrol. Returned to bike after paying, all the petrol is running out all over the forecourt!
The disturbance of filling the tank ruptured a rotting flexible pipe inside the tank that is part of the tank venting system.
First thing - make sure no-one's smoking nearby.
Get staff to initiate petrol-spillage procedure.
It all turned out OK but now I find that those submerged pipes were rotted by ethanol and it's not easy to find petrol pipe in the UK that is ethanol-proof on the outside. From Aprilia, MV and Land Rover forums I gather lots of others are finding the same.
So maybe it's best not to ask about ethanol unless you're ready to spend time measured in days researching the situation as it might apply to your own vehicle's make and age!
Otherwise - just go for it! With gentle driving! (And spare flexible fuel pipe).