After RAI, you will go hypo (not overnight) and then for the rest of your life deal with 'tweaking ' your meds until you are on a dose that you personally feel comfortable with.
You will deal with epiodes of hypo and hyper until the meds kick in properly and then it is up to you to try and find the 'right balance' of meds.
I had RAI (I was Hyper with Graves) and even though I have had a few episodes of hypo) it is now way as bad as dealing with hyperthyroidism.
read all you can, research all you can..log every symptom and dose you are on each day and then slowly you will find that 'happy medium'.
I would be a liar if I said this is easy as its not but i found a lot of easier than dealing with the see-saw of hyperthyroidism prior to RAI.
It does take time and it can take up to a year or even more to find the right dose of meds but this is also the case with a Thyroidectomy too.
personally you are in a no-win situation with Thyroidectomy or RAI.
They are both treated the same way except that RAI is less invasive.
If I had to have RAI again (for any reason) I would.
Hope that helps.