I had a decent paper filing system for our paper records so scanning them in wasn’t too bad. I did them in batches of like records so I could file them together easily. Most were in chronological order so I could keep them in order. Some I did in large bundles as I didn’t need the individual item as separate files. An example was my wife’s medical records from 40 years ago. There was important information there but we didn’t need each doctor visit stored individually so I scanned a few hundred pages into one pdf.
Speaking of PDFs, I store all records as PDF. If I get a receipt via email I save it in a PDF. Same for web pages I need to file. No problem reading them on any system anywhere.
Decide on where and how you want to store your files. I used a hierarchical file system similar to my paper filing system. Think about how you can get to them when needed. I keep mine in iCloud so I can retrieve them from my iPad or iPhone as well as the macs.
There are some documents you have to keep like wills, birth certificates, etc. Even though you are keeping the paper document, scan it in so you have an electronic copy. If you need the information from it but not the actual document it will be available.
Backup, backup, backup! Multiple backups using different methods. I use time machine, CCC, and Arq. Test your backups periodically. A backup that hasn’t been tested is not a backup.