Hello neokao,
Thank you for reaching out in Apple Support Communities. I understand you'd like to keep your options open, if you were to use an iPhone SE on either Verizon Wireless or AT&T. I know how important it is to view the best available options and I can help provide you additional information.
A SIM-free iPhone gives you the ability to activate the device with either Verizon Wireless or AT&T and is not locked to a specific carrier. You can read additional details through these two helpful articles:
- About the SIM-free iPhone
- Wireless carrier support and features for iPhone in the United States and Canada
For additional questions, I recommend contacting Apple for sales and product inquiry through this link here: Contact Apple
Kind regards.