I work as a personal property appraiser, and I've tried dozens of software packages. I keep going back to Excel, and now, Google Sheets. Literally everything else has too many issues and compromises, or no long term support. I've done archives with 20k+ line items, and for flexibility, portability, and simplicity, you can't beat Excel. If you want something pretty, you can use that data to populate a Word document, or import it into database software.
I wish there was a better answer, but I've yet to see it.
As far as what you need for estate planning and insurance, it depends on the insurance company. Most policies don't cover antiques and collectibles, so you might need a rider or specialized policy. Photos and an inventory are a good start, for high value items, you might need a professional appraiser. It all depends on your company and your policy.
Feel free to ask me any questions, I've been in this biz for a while, and I probably have some answers, or at least know where to find them!