I'm a I-751 survivor (using this term as a joke of course).
Nothing changes too much when you are a conditional resident with expired GC and valid extension letter. You technically have all the rights as a person with 10 year GC.
When you go through I-9 verification with employer, I always advice using US issued driver license or state ID AND unrestricted social security card. If you enter the US on CR-1 and never had SSN, this is the card you'll receive. Some HRs insist on seeing GC. They cannot do it by law. If you give in to their request, they'll be paranoid about extension letter and conditional card, so avoid showing GC at all costs.
You typically won't even use GC for anything other than:
- Proving your status when getting or renewing Driver's Licence / State ID
- Getting mortgage or loan, some lenders insist on seeing GC. With many online banks, you can open accounts without your GC being shared
- Travelling in and out of the US.
When travelling internationally, your online check in may not work. And even if it works, it doesn't matter as you still have to present GC and extension letter to airline staff upon check in to the flight to the US. Some airline staff may not be familiar with extension letter, so you'd have to ask for their manager. Overall, just make sure you arrive to airport ealier.
That's all I can think of.