Hi, i'm gonna answer some of your questions:
1.- This one seems to be related with the "Pre-Frames" render option. Try to change for 10,20 or whatever to see if that fixes the problem.
2.- Yep, basic shapes is just for that if you want more control you have to use custom sprites. Add X/Y scaling on basic shapes will see.
3.- Manual rendering is to create some effect and then pick and move the emitters to create movements with more freedom.
The .gif export is still a wip, we have to solve that blank frames.
About the +500 Sprites is my fault, just changed the desing and forgot to upload the zip with all them , btw, actually are close to 700 sprites. I'm gonna upload what i have now, and sorry for the incovenience.
The other technical question CodeManu will reply you soon.