This spectrum is good, but a bit prescriptive if you want to evaluate future schemes.

1. Can I get my money back? *

2. If not, it's custodial. You now need to judge by their expected value of preventing you from taking your money.

(* There are probabilistic schemes which can theoretically sit between these two)

"How likely are they to rug me" depends on many factors, most hard to quantify. In some schemes it's hard to stop individual payments without stopping them all, and/or hard to identify which funds to freeze. In others there's a bond which is sacrificed. Some rely on reputation damage.

These are only interesting because we will always need some system for sub-chain amounts.

I really like the idea of a "Nero protocol" where anyone who proves malfeasance by the custodian can burn the funds. Such proof may be impossible though (prove they refused to let you spend your funds?).