I suspect that you might need more memory for your database. It might be worth to move to a multi container setup so at least your web layer is more scalable.
My advice: resize your server to something (much) larger first, so all the after-migration jobs have room to run, and your users will not have a negative experience. Like Jay said, they will be vocal, and toxicity can kill your community, especially when performance is indeed bad.
Then keep an eye on things and see if you can scale down after a while. Just don’t resize your disk, so you always keep the option to revert and scale down again.