Part of the handshake process when building a pepVPN connection is for both sides to advertise all available WAN links. When using SpeedFusion (you can add a license to the B30 Pro for that BPL-031-PRO-LC-SF) the device at Site 2 and the FusionHub would create tunnels between it and all the available WAN ports on the B30 Pro. Without SPeedfusion bonding license, the B30 Pro will do SpeedFusion Hot failover so traffic can fail seamlessly between it and the FusionHub/BR1.
Peplinks Dynamic DNS offers a single domain name for your device but you can prepend that with the WAN link name too to be more specific (so mybalance30pro.mypep.link and wan1.myBalance30pro.mypep.link would both work for example).
If you do outbound PepVPN from both the B30 Pro on site 1 and a BR1 (as an example) on Site 2 to a single Fusionhub, then a tunnel will get created between each remote site LTE and the Fusionhub public IP. Traffic between the two sites then can happily flow over LTE at either site.
If both sites have LTE and both are dynamic and the PepVPN is configured site to site (rather than using the Fusionhub as a hub) then tunnels will only get built outbound from each LTE connection to the other sites other WAN links (that have public IP addressing that is routeable). If all wired WAN links at both sites fail then so would the pepvpn.
You can get public IP SIMs but I strongly suggest you don’t. Instead use a FusionHub.
Yes. In Network → Routing protocols ->OSPF & RIPv2 you can choose which subnets are advertised to remote peers.