[kixiQu]

Followed accounts are easier to do manually; there's a simple export / import interface that existed before the account move feature.

I will note that for you "as a content producer" the uniformly reverse chronological presentation on Mastodon highly penalizes older posts (even a day old!) to an extent that is pretty rough to get used to, and that makes those older posts pretty irrelevant to move over. This is much like Twitter before its engagement-maximization algorithm days, though.