Changed subsite to subdomain in MS Network Admin - bad idea?

I have a MultiSite that I've had for years. I have replaced/rebuilt a couple of the subsites ( on subdomains ( I did so to separate the sites due to plugins I use - to prevent conflicts and stress on the WP structure and so I don't lose everything if something goes wrong...Again.

What I did: I created independent WP installs on subdomains. In the list of sites in the Main MultiSite Network Admin, I manually changed the old subsite URL to the new subdomain URL.

Is that a bad idea?
- Normally a subdomain is not part of the MS Network at all.
- I don't want to create any weak or stress points in my main MultiSite by doing something odd.
- As far as file structure it looks the same - subsites vs subdomains, they're just folders at the same level.

Why? I did that because I want to access the subdomains via the Network Admin site menu (in the upper left corner.) It turns out that each subdomain connects to JetPack thru the main MultiSite Network Admin too. I don't know what that means.

How does a subsite differ from subdomain in an MS Network?
I am fairly new to subdomains. One subdomain integrated into the MS on its own somehow or I don't know what I did - that was some time ago. I liked it so I did it intentionally with another site.

I'd appreciate any input. I'm WP experienced but not very tech literate. Speak slowly?

Cheers! Thanks