In a perfect world it's all balanced as one rotating mass.
Now back to the real world, of a clutch change or flywheel change upsetting things, it won't make a noticeable difference at all unless you are hitting some seriously higher rpm than normal, remembering ford customers never complained about ford's std balancing.
If you've a spare flywheel though why not think about lightening as well before putting in ?
My 2wd one went from 8.9KG to 6.6KG, lighten/skim for £50, 6.6KG with ring gear I thought pretty good.
tabetha