Upgrading subscription – and what happens if you go down again

So far I've been paying the monthly entry-level subscription, which gives you eight characters total and they have to be on different worlds, and I'm at the point of contemplating whether to upgrade it to get the higher number of character slots.

Mainly I would like to know what happens if you go back down to the limited sub again after you've added extra characters to your account. Presumably some get shut off, but which ones are you left with? Earliest created, most recently used, or some other rule?

Also, can I upgrade in the middle of the month or would it not take effect until the next time I am billed?

Your characters will be locked except the first one in the server you choose. They don't give you the option to choose what character you want specifically AFAIK.

Not sure about upgrading during the middle of the month.

I think you can only play the first character that you made. If you get a 6-month subscription, it should be the same as the entry level fee on a monthly basis, except it's a standard subscription.

if you upgrade in the middle of the month it will take effect immediately. I believe any cost is prorated for time remaining with a minimum charge of $1.

if you go back, newer characters will be locked out and only the first one on the server will be playable.

if it works like everything else, if you upgrade, I believe they would pro-rate the upgrade, I think.

I know when I added another retainer for instance, they did not have one retainer that extended 15 days past the rest, they just charged for 15 days that month they were added, and full rate to bring them in line. I think subs work the same, you are charged for whatever percentage of the month that remains. so your expiry remains the same.

Thanks for the answers.