Transferring to Porkbun (or another registrar) adds a year to your domain registration, and your remaining time from GoDaddy moves over too.
For parked domains, you can either leave them with the default nameservers or set them up with Cloudflare but without any DNS records.
Cloudflare works well, but it can be a little complicated to set up. A simple option is to use InMotion’s DNS first, then switch to Cloudflare later—Cloudflare can automatically pull in your records to make the transition easier.
Keeping domains and hosting separate is a good idea in general, but for small projects, it’s not a big deal if you use your host’s DNS instead of a third-party service.
I recently moved my email from GoDaddy/MS 365 to Google Workspace, and I’m about to move my domains to Cloudflare. Cloudflare has detailed step-by-step instructions for transferring from GoDaddy, so that part should be easy.