Starting to invest €500/month – which exact ETF(s) for highest long-term return (with ticker/ISIN)?

Hi everyone, I am beginning a monthly investment plan of €500 via Scalable Capital with a long-term horizon (20+ years). I would like to choose ETFs with the goal of maximizing long-term returns (not short-term gains). I have two main questions: 1. If the goal is highest expected return, does it make sense to invest all €500 in one broad global ETF (e.g. MSCI World / ACWI), or is a combination of ETFs (e.g. World + Emerging Markets) likely better? 2. Which exact ETF(s) would you choose today, and please include the ticker and/or ISIN that is available on Scalable Capital so I can find them easily. I understand higher expected return comes with higher volatility and I am okay with that as long as the choices are evidence-based. No market timing calls please, just logical, long-term ETF selections. Thanks!