to answer your first question, it affects shift points overall, and thus it'll affect both downshifts and upshifts. if you're getting a delayed shift, you should check the adjustment of the cable.

if adjustment does not produce good results, check your tranny fluid levels, or if it's been a while since a flush, do a complete flush.

to your second question, the proper procedure to checking your tranny level is after your car has warmed up, you are to shift through each of the gears you have a few times. better yet if you have driven around a bit and the car has had a chance to go through every single gear including OD. then park it on level ground. while the car is still on, pull the dipstick and wipe, then put it in and pull it once more. read the level.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'