Even though this guide is referring specifically for Melomels (fruit meads), the principles are applicable for all meads (the only difference is that I'd double the nutrient amounts for non-fruit meads, since you aren't getting any nutrients from fruit in those instances). This is one of the best guides out there. I still reread it every few batches:http://www.bjcp.org/mead/melomel.pdf
Personally, I use Lalvin 71B for my meads. Any yeast will allow you to produce a sweet or semisweet mead without backsweetening, but you need to learn what its alcohol tolerance is for the meads that you're making. The only way to do that is a bit of trial and error, I'm afraid. For your first few batches, I'd shoot for an FG lower than what you'd like and then backsweeten to the level you're shooting for. You can always add sweetness to a mead, but you can't take it out if the yeast finishes higher than you'd like.
For 71B, my sweet spot for an OG is about 1.140. Different yeast strains will have different alcohol tolerance, so you need to do some testing. Most champagne yeasts are pretty alcohol tolerant, so I'd start at 1.130ish for your first batch. Figure out how much honey you need to backsweeten with, then add about 2/3 as much to your next batch at the beginning. By your 3rd or 4th batch you should have a good feel for what you like if you keep all the other factors the same (i.e., same fermentation temp and nutrient schedule).
Using staggered nutrient additions, you can have drinkable mead in 6-8 weeks. But these will be in the mid-teens ABV%, so they could always use some extra time to age and mellow out.
One more thing, you can't go by the manufacturer's recommendation for the yeast's alcohol tolerance with meads. Using proper staggered nutrient additions, you will generally exceed the yeast's listed ABV tolerance (sometimes substantially). For example, Lalvin states that 71B has a tolerance up to 14% ABV. My meads are typically around 16%, and you can get it up over 18%.
Honey can vary in sugar concentration a bit. 35 PPG is a conservative estimate. I usually start with that as a guideline, and take a gravity reading after I mix in my water. If I need to dilute it a bit, I do so at that time. I brew 1.5-2 gallon batches. I use a 6.5 gallon bucket for my primary, and mix the honey and water using the whisk attachment on my immersion blender. Make sure you have plenty of headspace in whatever fermenter you're using! The mead will foam up quite a bit as you aerate and add nutrients for the first week or so.
Good luck and enjoy. Meadmaking is pretty simple once you get the hang of it. And the results can be fantastic.