Thank you for asking. 

The main difference between this two models is the way to wear the tiny earphone. 

As you can see from the product, Although the panels of the two products are the same, the headphone compartment design is completely different. 

The X12 Ultra is using Earpods head design, we call it earbud. while the E12 is using "In-ear" design, which named as canalphone. 

Both of them are using the Qualcomm solution.

The X12 Pro and X12 Ultra are both multiple panel colors and Bluetooth 5.0 technically with Earpods head design at the headphone compartment. 

The X12 Pro is a market circulation model with Realtek II solution. Compare to Realtek I, Realtek II fixed all the problems encountered with the Realtek I. 
Differently, The X12 Ultra is an updated version, which loaded Qualcomm stero plus chipset. Optimized the connections and fixed all known problems. 

What's more, X12 Ultra is Aptx supported, Qualcomm® aptX™ audio technology powers hi-res wireless audio behind many of the world's finest Bluetooth® smartphones, speakers, transmitters. 

This absolutely meets most of sound enjoyment crowds.

Thank you for asking. The main difference between X12 and E12 models is the way to wear the tiny earphone. 

However, E12 ultra and E12 Ultra Glitter series are both using "In-ear" design, which named as canalphone. Also, both of them are using the Qualcomm solution. 

Moreover, the Main difference is the Glitter series molding with a high-end premium material, optimized and fixed the known problems. 

1, Disconnect and delete the Bluetooth device information on your phone.
2, Leave both earbuds in the charging case and keep it in charging status.
3, Long press both buttons for approximately 6 seconds. Release immediately when the lights flash.
4, Take both earbuds out, then wait it automatically pair and connect(The lights will flash alternately while paring).
5, Restore done, Please try to re-connect with your devices.