The hooha surrounding ethanol is it rots rubber and untreated aluminium.....but that's only the case with E85 and pure ethanol (E100). 5 or 10% dilution in petrol won't do any harm to anything. Long term fuel trims might go up a little bit with E10 as ethanol has way less potency than petrol. 10% is as far as you can without needing bigger injectors, so I doubt we will ever see E15 or E20.
Apart from the rubber hose feeding the low pressure fuel rail, everything in the fuel circuit is plastic, so that isn't a concern.
As for 95 vs 98,99 - if you look on the petrol cap, it says 98/95 Super Unleaded. Above '95' is a 'refer to handbook' graphic. What the handbook will say is, you may noticed reduced performance running 95....but what that REALLY means is, the chance of detonation is far greater. 95 works on a standard car, but won't make the same power as it would on 99 RON. Remaps almost certainly always need 99RON.
