I spend the bulk of my earnings on Mephisto (just kidding, bu they are pricey). I now buy size 9, but had been size 7 1/2 for most of my adult life. I, too, but gel innersoles, in the heels only. I like getting the shoe a bit bigger than I used to--it seems to accommodate the varius changes I deal with, and I can use all kinds of innersoles, or tie them tighter, when need be.

Everyone is different.

Mephisto has two lasts, one of which has a large and high toe box and is very very wide. The heel is normal; not wide. That's the one I use.

New Balance is also known for a wide toebox, and some swear by them.

If you have the finances to do it, I'd say I've learned that you get what you pay for, and the more expensive shoes have much better shock absorption, and last a lot longer. (I keep my mephistos for years and years).

For socks: There are various seamless "diabetic socks" online, and I've bought there. I think the consensus is against cotton. In winter, I like thin smartwool, but I've heard good cases made for acrylic.

there are sock websites.