What are the best practices for creating a Meta device?

1.The maximum size of an individual device that i can create on a vmax is 240GB. For example if i am creating a 250gb device, i can create this device using Metas. While creating the meta device should i create this device using meta members that are powers of 2-- 2,4,8,16 is that mandatory?

2. Say if i want to create 80GB device, can i use metas to create this 80GB device? Is there any size limit to create Meta device?

3. Are there any restrictions while creating Meta devices that get performance impacted and should not be configured?