Which domain regeistration / management would you recommend?

Apparently rout53 acts as domain registrar as well.

https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/do...

I'd say Cloudflare is a great option. They don't add any markup to the domain cost or have renewal fees. You just pay what is charged by registries and ICANN.

https://www.nearlyfreespeech.net/services/domains

I have almost all of my domains in Cloudflare. The only exception is one domain, whose tld is not currently supported by it... I am happy with it...

Avoid Cloudflare at all costs. They suspend peoples accounts for literally no reason(false positives) and stonewall them and delete their domains on short notice. https://news.ycombinator.com/item?id=31576353

google domains has been solid for me for 8+ years

https://domains.google.com

Cloudflare does cost.