If you are in Akihabara, Club Sega, Hey, and Taitio arcades are within walking distance of each other. You’ll pass them all walking up and down the street so you don’t need a guide or to remember the locations before hand. When I was there a few months ago everyone seemed to be playing the 3-d arena fighters like J-stars & Dragon Ball Xenoverse style. Some Gundam game seemed to be the most popular “fighting” game people played. There were a bunch of card based games that seemed to be popular too but I didn’t try any.
The 2-d fighter floor of Club Sega was virtually empty. I did see people lined up to play Street Fighter 2 but I can’t remember which arcade that was. I think each play was only 10 yen or something. I did see a decent amount of people scattered around different arcades but there were plenty of empty machines around. I don’t really have any Street Fighter specific advice but the business day in Akihabra seems to be Sunday so that might be when the heavy hitters show up.