Hello and welcome to Apple Support Communities, Fitzyscot!
We understand your iPad Air becomes sluggish or unresponsive when you try streaming something. We'd be happy to provide information to help you address this.
You mentioned that you've already reset the Wi-Fi. Did you mean you reset network settings as described here?
If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network
If so, you may want to try restoring to factory settings and testing to see if this continues with a new setup:
How to back up your iPhone, iPad, and iPod touch
Restore your iPhone, iPad, or iPod to factory settings
If after setting up as new, your iPad Air is able to stream correctly, try restoring the backup:
Restore your iPhone, iPad, or iPod touch from a backup
If the issue returns after restoring the backup, set it up as new again. It may be that the issue is located within the software with your current setup.
Let us know the results.
Have a great day!