I have a question. I’m on the F1-OPT. My employer offers me 401K matching contribution. As far as I know, I don’t get many deductions on the Federal Income TAX, because I’m nonresident. If I chose to contribute, will this contribution be taxed anyway or I get tax deferral like US residents?
I'm Brazilian resident.

The 401K contributions by you AND your employer are tax-deferred, which means that income tax will be assessed when you make a withdrawal from the 401K.

This applies irrespective of your visa status or whether or not you are a resident or non-resident.