18 wheeler..
As a longtime designer of loadsheets and other like instruments of the devil, I suggest that computer generated data ought to give you a much better calculated cg .. and hence better stab setting.
A manual trimsheet usually has a number of designed-in errors (normally accounted for by an adjusted envelope)to make it workable.
If designed well, the trimsheet will ensure that the cg is OK (ie within limits) but not necessarily very near to where the trimsheet suggests it might be. As a result, the stab setting will be approximate only - there is no point in agonising over the setting ..... sensibly close is fine.
The computer generated data ought not to have the errors which are usual in the manual sheet.
Standard weights are another problem altogether - although, if they be based on sensible population stats .. then the data are pretty good with reasonable numbers of people and bags. Best to weigh if the operation is very critical on weight.
And, do keep in mind ... the empty weight data is not all that accurate in most cases .. I have done a number of investigations in this area and there are traps for young players in weighing aircraft ....