For MTG proxies, you want at least blue/black core board, around 300 gsm and 0.3 mm, plus decent printing and cutting, to get close to real MTG cards in sleeves
One thing I did that helped was to find complete set lists online, and create a reference document that I printed out with the English names for all of the cards, broken down page-by-page of the binder
Using combat to take out Planeswalkers is always a good idea, but it means you might not be progressing your own game plan
If Henzie is in play, though, you're getting a slightly cheaper blitz cost even if you're on your first commander run
Standard sizes include Japanese (62x89mm), Standard American (63x88mm), and Mini European (44x68mm), but exact tolerances (0.3mm) are critical for snug fits