> 1. You can't run all the rules on your inbox to sweep the piled up email after a weekend reboot. No such option while it is still present in the legacy native Outlook.

I'm not sure what you mean. I have rules running regularly to move messages around, delete messages older than X in some folders. It all runs fine. Maybe there are some other kinds of rules I'm not aware of? But I do remember that back when "old outlook" was still the main thing, I needed to be running for the rules to apply, which meant that interacting with a different client was always... funny.

> 2. You have no option of deleting an entry in your calendar without sending a decline

Could this be a config flag somewhere? I've just run a test and invited my MS account from a personal mailbox. On the event, once accepted, there are two separate actions: decline and delete. I've received the "accepted" mail, but haven't received anything after "deleting" the event.