It runs fine on my Pixel 7a, I have an account with 2 Brazilian banks and they all work well.

Some apps just don't work though, but they are far and between, an example is Brazil's gov.br, which is a website that is used for ID confirmation on everything that pertains to the government (tax revenue, your own business details,etc.). But then an old phone does that job for me at home.

Speaking of Brazil, it is worth mentioning that Google Pixels are not officially sold here. The ones I did obtain I bought on a "Brazilian eBay" and there is no e-SIM support for it nor any warranty services. I had to do the battery replacement myself despite knowing that Google was offering to fix faulty Pixel 7a's on NA/India/Europe/etc. I am only bringing this up because, coincidentally, 50% of Motorola's smartphone sales are on LATAM. It's a pretty smart move they are making if you ask me, they are aware they could explore this huge market it seems.

I haven't had any trouble with banking apps. One gives me a warning but allows me to continue. Google Wallet doesn't work for payments but that is just fine with me.

My bank's app won't run on my Pixel 8 Pro with GrapheneOS. Most apps run fine. It's pretty much just the bank app and eBay that refuse to run.

Use your bank's web portal. If your bank doesn't let you use a web portal, switch fucking banks, because that means they don't care about you.

Bank apps are filled with all kinds of tracking spyware.

Anyone with first-hand experience, how’s Graphene OS with banking apps?

Depends on the bank. Chase didn't work, but bank of america did.