To see how these worked and what was available, it was necessary for me to open an account. TIAA does make some additional funds (or their institutional share class) available NTF. But there are so many oddities that you must really want something they offer to go through the effort of working with these accounts.
TIAA IRAs are structured as annuities with a brokerage window. So when transferring cash in, it technically goes through the annuity into the brokerage account. More importantly, I believe this means that one cannot transfer assets in or out in kind.
In order to actually have access to the annuity funds (mostly CREF funds), you have to have some relationship with TIAA's employer plans. You might have a 403(b) with them yourself, or you might be related to someone who does. If not, then while you can open the IRA annuity with TIAA, you won't be able to invest on the annuity side.
In order to get a brokerage window, TIAA will "qualify" you. This makes no sense to me. I could understand TIAA "protecting" you from yourself if this were an employer plan, where the employer has liability. But we're talking IRAs here. When one goes to, say Schwab, one opens a brokerage IRA, period. No qualifications.
As part of that qualifying process I had to declare how much (roughly) I expected to put into the IRA and upload a statement showing the outside account from which the assets would be transferred.
It took three days for the brokerage window to be up and running. (I haven't funded the account.)
The short term trading period for NTF funds appears to be six months. On the plus side, the min investment for a fund is $500 unless the fund requires more. The fund screener (not accessible until you have a brokerage window open) won't tell you whether a fund (or share class) is open or closed. You have to do research on your own or call TIAA and ask.
I checked on a couple of popular funds here:
PRWCX - it would have a $1K min in an IRA and $2.5K in a taxable account (same as Fidelity), but of course it is closed. I had to ask.
CQTRX - $500 min (TIAA brokerage min); this has a slightly lower ER than COTZX which is NTF at Vanguard
GLIFX - $500 min in IRA (TIAA brokerage min); NTF