How do you start Citi Custom Cash stacking?

I think a CCC stack is probably the way to go for me as far as cleaning up the 5% gaps in my setup, especially after the nerfs to the BofA CCR and the waitlist stuff with the 5321 SYW (transit and EV charging are the next two categories I’m targeting)

What’s the SUB churning order and velocity for picking up new CCCs? Hearing also that Citi allows product changes in the first few months of card ownership without SUB clawbacks? Is there an upper limit to how many of these cards you can stack, and how do you differentiate them in Apple Wallet?