Withdraw H1-B before start date - Nonprofit CAP Exempt

[Adit Sanghvi]

Hi,
I am on OPT with 2 years of STEM extension available. My OPT is expiring in July, but my employer does not want to use STEM extension and wants to file for H1-B nonprofit, which will be activated on OPT end date.

I want to preferably get for-profit H1-B or use my STEM extension.

Can I allow my employer to file this H1-b for now? If i get a job offer and switch before July, will they cancel the petition or am I stuck?

Please help,
Thanks!