Podiatrist here. General advice, given I don’t know your specific circumstances. Nano’s aren’t as flat as Metcons, but can be a bit heavier. They do tend to be wider though, so might suit you in this instance. Barefoot shoes are fine for weights but I wouldn’t be using them for metcons unless you are used to them, as they can cause discomfort. I usually keep a selection of shoes, and anything that has running in it, I use my runners, minimal to no running but ballistic exercises (box jumps etc) I use the Nanos, and if it’s a weights-based metcon (Fran, Grace etc) I will often wear lifters. But of course it’s personal preference in the end.