I use Lalvin 71B for all my meads, but only out of familiarity. Basically, I plan on letting the initial ferment go to completion, then sulfite/sorbate, then backsweeten. If you're sweetening with honey, then just target the FG you want from the initial fermentation and add honey to taste.
If you're planning on backsweetening with fruit, then a little math planning is needed. You need to know your target FG and the gravity of the juice you're using. Then you can calculate how much juice you're going to use as a ratio of the final mead. Your initial ferment will be diluted by the same amount, and the ABV will be diluted as well.
It may be easier to talk through an example
Say you're making a Zombie Killer style mead and will be using a 1.056 OG apple juice to backsweeten. You've decided to target an FG of ~1.012 and assume that the initial fermentation will finish at 0.998. That means you want to add 14 gravity points to the finished mead. So 14/56=0.25 - you will want a quarter of your finished volume to be juice, and 3/4 to be your initial ferment. If you're targeting 6% ABV, then the initial ferment should end up at about 8% (4/3 * 6). That's about 1.060 for your OG, if you plan on stopping at 0.998
Now all those details will need to be dialed in, or adjusted on the fly. But basically, plan on the fermentation finishing just under 1.000. The target backsweetening level will vary depending on your tastes and the recipe, but figure 1.012-1.020 to be a good starting range. Use your palate as a guide, but take notes to be able to refine your process for future batches.