A single wildcard CNAME that points to your domains A record is easier to manage I would say. This comes handy when you add a new service to your stack, as you dont have to go and make a new subdomain record.

You already seem to manage all subdomain updates with that script, so it won’t help you much with dyndns. That is, unless you hit a rate limit when trying to update a very large amount of records at once.

Keeping separate TLS certificates is a separate topic from having a single wildcard CNAME record. Separate TLS certificates offer a slight security advantage, as a single leaked certificate secret wont compromize the rest of your sites.