Hello Patrick,
using PVST+ between EXOS 16.2 and Cisco IOS should be possible. One caveat is that Cisco PVST+ comprises an additional standards compliant rapid STP instance, and this needs to be added to the EXOS configuration as well.
Some time ago I have successfully tested PVST+ interoperability between EXOS 16.1 on X460 switches and Cisco Catalyst 3560. Please see
https://www.unix-ag.uni-kl.de/~auerswal/exos-cisco-rapid-pvstp/ for all the details, including the tested configurations.
Hope that helps,
Erik