I have a pair of the slip ons. I wear 9.5 in vans and 10 is what I consider my TTS and I wear a 10 (43) in these. I’d probably suggest going with a 10 for you.
I like Charles Tyrwhitt for dress shirts. They have several different cuts, including super slim fit if you’re skinny, and a few different styles of shirts. They all come with collar stays and can be customized (pockets, French cuffs) and you can also choose the neck size/sleeve length that fits...