Data Only SIMS - Any Technical differences with CGNAT etc?

Hi Everyone, 

Does anyone have any knowledge on SMARTY's Data only SIMs? Is there any difference in the way CGNAT is applied?

The reason I ask is looking for a backup solution to my FTTP, the main requirement is being able to use VPN to connect to my workplace. This is using ivanti client in ESP protocol which I have read doesn't play nice with SMARTY's standard CGNAT deployment. This is also my experience with EE who use CGNAT and IPv6 which causes a timeout every 120sec.

Cheers

Pabs