What you are looking for is very possible. Key things when choosing an edge device is form factor, router throughput, VPN throughput and interface count (both how many cellular but also how many wired WAN and LAN Ports.
The physically smallest that supports a single LTE and BGP is the BR1 MIni
But it needs an additional license to enable speedfusion technologies (not bonding, but hot failover nd wan smoothing/forward error correctino) and the wired WAN (out of the box only the cellular WAN is enabled).
What sort of traffic is it you need to support? Do you need bonding or is ti more about simple failover between WAN and LTE?
BGP is supported on all MAX routers. BGP on the wired WAN will work fine, using BGP on the LTE connections - especially if you want to bond those is a trickier question - but perhaps you plan to just failover to a different non BGP managed IP when on cellular?
Suggest using FEC in the SpeedFusion config for RDP and VoIP when on cellular it really helps.