Kudos for mentionning powerDNS, it’s an amazing software :)
One thing I love with powerDNS is the various backends available, notably the postgreSQL and mariaDB/mysql ones. Only the primary powerdns instance modifies the database records, the secondary instances just read from database (master or replicas). Thus, no real need for AXFR: as soon as you added/modified a record on the primary, the secondary pdns servers will see it in the database.
The pdnsutil CLI tool is also really convenient, and the powerDNS API is a godsend when you need to automatise stuff for thousands of domains and hundred of thousands of records. There’s also a nice third-party webUI (powerdns-admin, docker image: pdnsadmin/pda-legacy). Bonus, Terraform does have a powerdns provider.
At work we use dnsdist (from powerDNS too) to load-balance between our powerdns instances (with caching!), and to filter out/rate-limit/temporary ban bad actors (dns laundering, records enumeration and such for example).
1Gbps down/700Mbps up here, 35€/month (another french provider), no data caps - for 5 bucks/month more I could have 5Gbps down/1Gbps up, but… well, my home network is still using 1Gbps switches - but all the cabling was built with 10Gbps in mind.
Data caps are pure robbery. We run a non-profit ISP/hosting platform and a non-profit IXP with friends in West France, the only thing you pay (and the only thing end users should have to pay) is goddamn bandwidth.