One thing to consider when using Opnsense or OpenWRT is the increased number of devices you need. Depending on your needs you quickly end up with 4 devices (modem, router/firewall, access point (wifi), SIP telephony). With a bit of luck you can unify the first three with OpenWRT on a suitable device, but with Opnsense you likely end up with all four. All of these cost money, both in terms of buying, but also electricity cost. All need to be kept up-to-date, understood and debugged in case something breaks. So I would try to keep device numbers low as a beginner and search for a device which offers the first three mentioned functionalities, and that's something you won't succeed with with Opnsense.