To write the tag, use the app NFC Tools to do the writing as it is versatile and needs no special permissions.
Using NFC Tools, use the Write tab, Add a Record to add these two records:

• URL / URI: wifi:networkname/wpa/password
• Application: com.wifitap.android

Then, write the tag.

Finally, presentation is a good thing.  I've attached two sample files to this post showing sample text and a sample QR code.  The PNG is a simple PNG file.  The SVG file is an InkScape SVG file.