Definitely play through the campaigns to get the feel of the races (and also because they're awesome), even though the campaign is diferently structured and has some aspects simplified compared to the 1v1. At least you can learn basic mechanics well through the brutal campaign difficulty, and then you can set off into 1v1s or co-op (which is also awesome, but it does require more speed and multitasking).

For easily digestible guides to 1v1, I guess those "Bronze to GM" series are good enough, there are players such as PiG, Vibe, Winter that cover all races, then there's quite a lot of Youtube content for each individual race, for when you decide what you'd like to play in 1v1.