If you want buy eth and btc for long time investment then there is no need for research. For a beginner investors make us sure best investment for both currency. Even if you have extra lot of money then you can follow cmc top list to buy good coin. But my suggest don't invest in meme coin and new unless coin.
There is no need to doubt Bitcoin and Ethereum for investment, but that was before,
now we also have to do research first such as technical analysis research,
if TA is not carried out then of course it will also be risky even though BTC and ETH are the top 2 cryptocurrencies.