If you have a static IP address, you can just use A records for each subdomain you want to use amd not really worry about it.

If you do not have a static IP address, you may want to use one single A record, usually your base domain (example.com), then CNAME records for each of your subdomains.

A CNAME record is used to point one name at another name, in this case your base domain. This way, when your IP address changes, you only have to change the one A record and all the CNAME records will point at that new IP as well.

Example:

A example.com 1.2.3.4

CNAME sub1.example.com example.com

CNAME sub2.example.com example.com

You’d then use a tool like ACME.sh to automatically update that single A record when your IP changes.