Personal preference on NRT is ANA - the UA F lounge isn't anything special and has a worse premium drinks selection - however the food is more western if that appeals. The ANA lounge is quieter, was closest to the TG flight the last time I visited and has a noodle bar for a nice touch.
As for pre-ordering your meal, I'd just browse the Thai list and choose something you like, from my own limited experience (5 trips in TG F, pre-order each time) the best choice I made was the Tom Yum soup from BKK - lobster has been ok but dry. I don't think there is a clear winner from my own reading so best to just choose based on personal preference - or go for lobster since it is 'more expensive'...
