I'm interested in the specific claim that Congresspeople are trading in ways that beats SPY, and I think it's just not true.

The Unusual Whales piece says that in 2023, Democrats had 31% returns, Republicans 18%, and SPY was 25%. Doing a weighted calculation, I get (31212+18222)/(212+222) = 25% exactly. So that piece provides some strong evidence that in that year, Congress did not outperform the market, despite attempting to imply the opposite.

Your other links are just general speculation on the subject, and in fact link 4 even says "House and Senator stock returns are consistent with random stock picking."

I do think Congress should probably be restricted from options and maybe short-term trading in general. But I get frustrated by all these doomers who think Congress is corrupt and doing insider trading all the time when there's just not any generalized evidence for it.