Where to find all/most variants of a glyth?
i would use 教育部異體字字典:

http://dict.variants.moe.edu.tw/variants/rbt/home.do

it's authoritative, and most comprehensive.

eg 御 (u+5fa1), it listed 37 variants :)

http://dict.variants.moe.edu.tw/variants/rbt/word_attribute.rbt?quote_code=QTAxMjk1

have fun :)