Accumulating vs distributing: accumulating classes reinvest dividends for you; distributing ones pay them out as cash. Same fund underneath.
Currency: the ticker's currency only affects how the price is shown. What matters is what the fund owns: mostly overseas companies, so the pound's moves affect your returns.
Fees compound: a 0.1% difference looks tiny, but over decades it adds up. That's why the fee over 20 years is shown above.