how tight is too tight?
Probably something that doesn't come off while walking in tall grass, but does come off quick when you want it to, also fast to tie up again is the knot you are looking for.
I usually prefer Ian's Secure knot. Such a brilliant link!
There is a pair of shoes which have a slightly longer laces which I deliberately didnt change, with them I use Mega Ian's knot.
I don't know if anybody has tried the method below or not, but this worked for me:
I have shoes with ankle support (whether they are good or bad is different question), When I am done tieing the shoelace, I do a bit of stretching and see if it restricts my ankle movement by any means. If it does, I loosen it up a bit and then I am good to go. For what I have observed, if you tie up too tight, with usual hiking shoes you won't feel much of a difference in the tarsal region and overall foot, but you will where the neck of the shoe comes in contact, either near the ankle (if they are not ankle-high) or above the ankle where the shin begins (if they have ankle support).
A side-note: Elasticity of the shoelace also comes in picture when its about how secure a knot is!