Issues resolved.
The false No Internet access message on guest network was due to firewall rules to force using internal DNS server. There was, also, a typo on DNS server at guest dhcp (157, instead of 168).
Set Slave Static on CAP on hAP ax2 and interfaces names doesn't change (so often).
First internet connectivity issues of all WiFi were due qcom driver on Mikrotik. It not allow to set VLAN on datapath.
Will continue tunning and restore pieces from old configurations, improve VLAN filtering, but VLAN issues are gone, I really hope.
Thank you all very much for yours support!