Do you use an umbrella LLC? Questions about branding

Do you have a single LLC that you keep all of your products under?

When it comes to branding - do you buy a domain also the LLC? Does the TLD matter much? for instance if .com is unavailable, would you prefer .app or .io?

If you pick a double word LLC or a domain for your app, what are thoughts on scenarios when the first word's last letter is the same as the second words first letter?