[Users] Information request

[o1bigtenor]

Greetings

Have been running gmail accounts for a long time but am very tired of
their social experiments so I am wanting to transition to claws.
(Claws was recommended by a buddy as a very useful well set up text
based email program.)

I have some possible issues - - - my two primary accounts are NOT
small - - - - one is just shy of 15 GB and I've got to do something
sooner rather than later. I've also been bitten in the past trying
things and jumping in when I didn't really have enough background
and/or knowledge to do a good job - - - - therefore I'm asking
question(s) to hopefully reduce the pain in transition.

My large account - - - - can I move say the oldest 2 or 5 GB first and
then move the reset in 'chunks'?
Given such large volumes of emails - - - is there a preferred setup
that would minimize possible problems?
Any suggestions from 'power' users re: any other pitfalls?

TIA