One problem I see with .im is it's from a different country than mine and they can change the rules to allow only residents or so, or they can hike the renewal cost to something really high. Also, I am from India where .in is common so some people might confuse .im for .in. I am inching towards <9 char>.in or <9 char>.net (my first name), but then I am not sure whether I should give up my <4 char>.im (my nick name).
Also, mailbox.org supports up to just two domains in the plan I am paying for.
The last thing you want is your emails going to a wrong tld:
going to
is very likely in your scenario for less tech-savvy contacts IMO.
I think I will keep first-name .in and .net and let the nick-name.im expire after a year or two and share .net email to my contacts.
I have catch-alls set up across several domains I own, they all go into one inbox and replies etc. are sent from the same email the original was addressed to, automatically.
I usually use one domain for casual use (like games, Twitch, anonymous services), one for semi-professional stuff (with my real name), and one for actual business.