Best article I've read on tuning:
Tuning - The Carver's Almanac
Personally I'm suspicious of adjustable edgers but I suspect that a good quality one works fine. Most of the ones I see are cheap ones that come with "tuning kits", little bags of shiny trinkets you buy on EBay and then realize you should have bought the iron separately and then bought the proper tools from a shop one by one.
Not sure what you mean by base flattening, I am a firm believer in base structuring where grooves are ground into the base to promote water channeling under the board. Especially critical in spring.