what is better bridge mode for hotspot RSTP or None ?
Depend on what you want to use it.
As long as you make sure there are no loops in your network, the (R)STP will not bring any advantage. (but will not do any harm as well)
If you ask about performance, there is no difference between those modes. Only difference is ability to detect and prevent loops in network topology.
i use it for hotspot
Like here, in this case you can play with none:
https://wiki.mikrotik.com/wiki/Manual:Basic_MPLS_setup_example#Loopback_interfaces