Take a look at the short videos that I've uploaded. (just 3 seconds clips, so Loop it and focus on Propeller motion blur) is insane.

Now, issue #1, I was rendering this tests at a very small resolution and very low sampling, for previewing purposes.
But Around frame 80, it pretty much got stuck computing, and Ram memory was at 99%.
I wonder, if there is a way to optimize, Motion Blur calculations a bit more, or if I have any parameter missing or wrong. I've uploaded my motion blur parameter, I'm not using Velocity. Just Motion blur node inside Solaris.
As I need Super high quality motion blur, I used the maximum Subframe samples that XPU is allowing me, which is 8, beyond that all geometry disappears, which is also my second question... XPU only allows 8? ... when I switch to CPU, samples are pretty much unlimited. but of course it renders way slower. But I'll say XPU with only 8 samples, is giving an excellent result so far. wish I could go up to 10 at least.
Anyway, if someone is familiar these issues, I'd love to read some insights on them.
Thanks to all in Advance.
Cheers