@_astronoMay some others have also replied, but here are my two cents (I have lost count how many times I've moved accounts).
- you don't have to close this account. You can mark your account as moved, and still read all the old posts. See for instance my (first? second?) old account:
https://elekk.xyz/@aetios-importing your followed accounts is dead easy
-Mastodon also redirects your followers quite well, other fedi softwares lag a little behind or simply don't implement follow redirection, so in my experience it's best to create a notice post, pin it, and boost/re-boost it several times over the course of a week. (this is probably the most annoying part. in my experience though people tend to re-follow very well, and those that don't generally didn't interact much anyway)
-as others have noted though, you can follow everyone around the fediverse (with the exeption of instance blocks but they are fairly rare) so you don't *need* to move if you want to follow the action.
-that said, the platform thrives when people decentralise, and you are on the biggest instance. :)
-finally due to the sometimes fallible nature of fedration you might miss *some* of the action if you're not on the same instance. I think between the two mastodon instances that are affected here though it will be exceedingly rare though.
-bonus:
astrodon.social won't become slow if something happens with twitter again

See you around, love to see all the initiatives pop up left and right in this activity surge.