I'm only speaking of owning ETFs here, not the underlying securities.
TIPS fit the 'store of value' part of the portfolio. Where you won't make much, but you won't lose much either, and if there is sustained inflation, you should make real, after-inflation money. Whereas with regular Treasuries when there is sustained inflation you will lose money.
For example:
1 year returns:
Straight Treasuries: -3.3%
TIPS: +3.5%
The difference is because of the 'add on' you get with TIPS when inflation rises.
TIPS work the same way as iBonds...you get a regular base rate, then they add on a rate corresponding to the inflation rate.
The bad part of TIPS is that the base rate is negative right now. So you rely on inflation to get you above 0% return. If there is no inflation or there is deflation, you pay the government money to own TIPS. iBonds don't do that...the base rate will never be below zero so you can't lose nominal money.
Hard to say what TIPS are paying now, because they adjust to the inflation rate constantly. They don't pay regular, steady interest like straight treasuries. The amount you get from them will vary each month. The 12 month yield is 4.3% right now, but that's because of the huge surprise inflation we got. That will likely change.
I guess the idea of TIPS instead of gold is that if you want protection against inflation, TIPS are better because they almost always pay interest, while gold does not.