As mentioned earlier I prefer higher octane in the Plus8 as it seems to keep the MIL fault away. The extra detergents and less ethanol are secondary but nice to have.
The Gems system is reputedly slightly adaptive to driving conditions but not hugely so.
My preference is due to having tried higher octane and liking the cure it gave and the potential for cleaning the fuel system. I didn’t expect better performance as the ecu /map are standard.
The Millers experience with the Focus and my mate’s non improvement in his golf shows how fickle things are. So...you pays your money and makes your chouce.
I don’t worry about putting 95 octane in the Plus8 if it is the only available. Perhaps changing to 99 octane on alternate tankfulls might be a compromise. It is not abig deal.
