Working between fresco and illustrator - loss of resolution

I'm a new user of fresco and have noticed the following (note that all these comments refer to using vector brushes only):
- if you merge layers the resolution goes way down (so if you later try to increase the size of an element it is pixelated)
- but if you group all layers instead, there is then no way to group select the layers and increase their size all at once (that I can see - ?)
- if you export multiple layers to Illustrator for ipad and one of the layers was the square with the arrow pointing down (sorry I don't know what this is called! but it prevents anything going over the lines of the layer below) then that automatically reduces the resolution for the whole image. 

Am I doing something wrong here? It seems that if you just export 'normal' vector layers you can increase the size no problem in illustrator but if you have merged layers or draawn on top (that sqaure with the arrow thing) then you are limited to the size you created the art in originally in fresco and the layers are now pixelated. Is there any way around this? 

Do people working between the programs export the basic fresco layers and then do further on illustrator? Can you get similar results just working in illustrator for ipad if your focus is vector brushes? 

Any help appreciated!