Do I need a will, and what about nominees?

Yes, and the two are not the same thing, which trips people up. A nominee is only a custodian who receives an asset to hand on. A will is what actually decides who inherits. Without a will, your estate is divided by default succession law, which may not match your wishes and can be slow and messy for your family, especially with illiquid startup equity in the mix. A simple, properly signed and witnessed will, plus correct nominees on your accounts and a clear list of what you own and where, saves your family enormous difficulty. Founders with real equity should not leave this as a someday task.