What happens when i remove/delete my old iPhone from my Apple ID account? Secondly, what happens if I remove it from iCloud account? Pls RO below for explanation to questions

What happens if I remove a no longer used iPhone from my Apple ID list?

I recently switched from a 4-year old iPhone to an iPhone 11 Pro about 6 months ago. Backed up to iCloud prior, of course. I simply just swapped out my SIM card from the old one to the new one. Both unlocked and purchased directly from Apple store, if it matters. I am using the same iCloud/Apple account login/ID, etc, on my newer iPhone as was used on the old one. I also use, and have used, the same Apple ID on both phones, including iCloud and iCloud Photos — or whatever iCloud Photo Library is now called — Music (NOT Apple Music- just OG Music app from itunes), iTunes Match subscription, iCloud Notes, Messages, etc.

So, what happens to all that data/photos/everything associated to the old iPhone in my Apple/iCloud account? Will I lose stuff? Am I at risk of losing my Music purchased from old device and my Photos/Videos, etc if I disassociate/delete my old device? I can’t find much about this.

Likely unrelated to but possibly FYI: my old iPhone in question simply turned off and stored at home — I NO no plans to ever sell it so wiping it in terms of ownership/sec/Privacy risk is not an issue I don’t think.

Thank you!