Stupid routing question (/31 from ISP and then routed /30)

After posting about the ancient router that an ISP reseller has sent us for our shiny new 1Gbps line, I may be in the market for a new router.

I thought it was worth making sure I understand this fully. This is how things would fit together if I don't change anything:

The fibre will be terminated on an ISP supplied switch, which will then connect to a Cisco router. The 'WAN' side of the Cisco is x.x.x.129/31 The 'LAN' side of the Cisco is x.x.x.133/30 and will serve as our GW The one usable IP is x.x.x.134/30 which I can assign to our pfSense firewall.

So, I get how all this works. However the supplied Cisco clearly isn't suitable for the job. Either they replace it, or I'll have to.

If I replace it, I could get a Cisco (expensive) so I'm currently thinking more along the lines of a Ubiquiti edgerouter 4.

Or.. Is there a way to just skip the separate router and go straight from ISP switch to pfSense. I guess I could put the pfSense WAN interface on .129/31 and ignore the rest? Or maybe treat the WAN side of pfSense as a /29? Not sure that would work as presumably the ISP is using a /31 mask on their side. Is there a way to use both the /31 and /30 on the WAN side of pfSense and avoid having the router in between? Am I mad to consider it? I'm happy having a Cisco or Edgerouter in between, but it just feels like it's a bit of a waste.