I can only answer about the longarm. Longarms are designed to do bedspreads -- big, fluffy, polydown bedspreads. That was one of the original uses. In the old days they were called Industrial quilters ;-). I bought mine 20 years ago from someone who did nothing but thick bedspreads on it for the home dec industry. 5 oz definitely won't be too much for a longarm ;-).
Here's a description of battings, which will tell you that 5 oz is pretty much on the low end of thickness.
https://www.createforless.com/buying...right-one.aspx