Is your “normal” shoe a shimano shoe?
If so, I would say no more than one size and the would depend entirely on how your current normal shoe fits. I would say try some at your LBS and if your LBS doesn’t have the stock or won’t get them in without a commitment to buy, order from an online retailer with free returns and get a few sizes in to try at home.
With the mw81 I find them warm enough with summer socks until it gets icy, and then i use wooly boolie thick merino socks so you don’t need a boot that is huge for them.
Make sure you have your winter socks with you when trying on.
One more thing to consider; if you go too large with the shoe size, you may find you can’t get your cleats far enough back to be under the ball of your foot.
Bit of a long winded reply, hope it helps. I would get off my arse to look at my shoes but you really need to try em on 🙂