Indeed. But for 1500 USD I can build a brand new small form factor pc with 96gb ram and lots of compute power. Well if it works for you, great. Certainly looks cool

What is the benefit of using raspberries for your use case. Low power usually comes with low performance. Or am I missing something? If I invest the same amount of money in different miniPCs (used on ebay or similar) wouldn’t I get more compute power for the money?

Tdp seems fine to me for psu sizing. At the end of the day the psu may have some overhead anyway. You may want to look at pcpartpicker. They provide an indication of psu capacity