Really, that's all I want to know. Whenever I try to make it with the store bought "dry" noodles and soak my dish comes out terribly.
What are the best sauces to use? Best way to keep the egg from clumping? etc?
In my experience fresh rice noodles are ready to go and can be added to a stir fry without any perparation aside from cutting them into properly sized noodles (if they are purchased in a 'slab').
Any sauce you favour can be used on the noodles (adding additional liquid to the stir fry aside from the fat helps them to 'unroll'), an old favourite of mine for hangovers called "drunkard's noodles" involved frying onions and chili peppers in oil, adding the fresh noodles, then finishing off with soya sauce, lime juice, basil leaves, chopped tomatoes and chili sauce.
I live in Thailand so I feel I'm qualified to answer this question.
The key sauce for pad see ew (ผัดซีอิ๊ว) is figured out from the dish's name. See ew (ซีอิ๊ว) is a Thai soy sauce that is either dark or light and sweet or salty (yes, four versions in total). The dish also contains fish sauce.
In my opinion, pad see ew tastes best using the dark sweet sauce, which has a deep molasses flavour.
Use only sauce made in Thailand and there are no substitutions. Look for this on the label: ซีอิ๊วดำหวาน (dark sweet) or ซีอิ๊วดำ (dark not sweet). Since you probably can't read Thai I suggest you play a spot-the-difference game.
My personal favourite is this sauce but it's hard to get outside Thailand.
If you do substitute using normal soy sauce you pretty much end up with pad khii mao (ผัดขี้เมา).