Recently, I saw a bunch of people watching whale addresses and preparing to follow trades.

For now, I mostly hold back... To be honest, you need to first figure out whether they are building a position or hedging.
My previous approach: seeing large transactions entering exchanges and getting nervous to chase, only to often follow right into someone’s hedge;
Now my habit: first check if they have positions on both sides, whether they are opening shorts/buying protection at the same time, on-chain movements don’t necessarily mean “bullish,” it could also be moving collateral.

By the way, these days, the debate over privacy coins and mixing coins’ compliance boundaries has been quite intense, and I’ve become more cautious: some “whale movements” are actually just managing risk exposure, not sending signals to you.
Anyway, I used to split addresses and do small-scale trial and error; if the cost is manageable, I do it, if not, I pretend I didn’t see it.
Let’s stick with this for now.