Can I delete "start new backup" later if I want to keep it awhile?

I migrated from a 2014 MM to the new one. Whoopie! The migration process was a bit tricky with one monitor, one keyboard and Q&As from both computers.

However, I haven't done a backup yet. I understand the "claim existing" if I'm not going to attempt to use the old Mac mini again. But, I'm keeping it around for awhile "just in case."

I understand the "start new" keeps the old one available and a new one is started. I'm assuming that's if the 2TB external has enough space for two. Right?

So my question is: If I want to do a "start new" keeping the old backup "just in case" if I need to reconnect the old MM, can I, in the future, delete the old backups on the external that has the "start new" MM2 back ups on it? Or, when I start to run out of room? Or, will TM get all wonky because I'm trying to delete old TMs on it by "just simply" dragging to the trash. Or, if there's a secret in how to delete them later.