You are the only one that I repeatedly hear saying that a Raspberry Pi isn't enough. The people I know personally in the Bitcoin community run just fine with Rsapberry Pis - and cpu/ram usage is never a complain.
From experience chatting with friends and my own experience, I have heard bad stories from some, and I'd say:
Go with top of the line everything for a RasPi setup, good, large SSD, most RAM you can configure. What I think is not really sensible is thinking it's possible to DIY and use the cheapest configuration that 'technically works'. This is still a cheap setup for a hobbyist ... but it's not that cheap! It's not something a 14 year old can set up with a couple of weeks' pocket money :)
bitcoind especially, and to a lesser extent LN node, plus all the extras people inevitably end up installing ... it's so easy for the hardware just not to be able to keep up.