Welcome to the fun. I am a couple of years further down the track than you but still "beginning", as I had produced some fairly ordinary results before discovering HBT.
Your Granny Smith brew is similar to what I did in Fall 2017 (May, here in Oz). Mine was 2/3 Granny Smith, 1/3 Pomme de Neige (because they are among the trees that I have in our small orchard). Grinding and pressing your own is theraputic and thirsty work!
The Granny Smith cider was a two litre trial batch with EC1118, fermented at 60 degrees F and bottled after two weeks in primary then six weeks in secondary which by then had run down to 1.000. Using Brewers Friend Calculator, 14g of sugar was added at bottling for a planned 2.5 vols of CO2. I now simply add sugar, FAJC and/or plain juice to increase gravity by 2-4 points above the stabilised FG for carbonation when I bottle.
I tried a "Granny Smith" after about a month and it had good petilant carbonation, dry, tart, and a bit acidic but O.K. and very clear golden yellow.
Fast forward 14 months and I opened the last one this week. Much improved with the strong tartness gone and just nice Perlant carbonation... time does wonders!
The apple trees have been full of blossoms since early Spring and with only mild frosts it looks like a bumper crop this year. Typically my juice can range from OG of 1.055 to 1.075 so the resulting ABV can be anything from 6% to 8%.
I plan to bottle some batches at around 1.010 then stove top pasteurise at around 1.008 which I hope will retain just a touch of sweetness and perhaps drop the ABV a bit. The current batches from April 2018 are now six months old and are based on SO4 and WLP773. With these yeasts they seem to have retained just a touch of sweetness/appleness after having stopped at around 1.002 then had FAJC and unfermented juice added to bring them up to 1.005 for bottling. Carbonation is Petilant at this stage and they are "drinking well".
Another 2 litre "trial batch" from 2018 is Cherry Cider on SO4 with 250g of (our) frozen cherries added to the juice of 5kg of mixed Pippins, Pink Ladies and 1kg of Beurre Bosc pears. This lot started as a trial to see if the sorbitol in pears would give a bit of sweetness but the temptation to add the cherries to secondary was too much so there are two variables in the "trial" (pears and cherries) so I don't know which had most effect on the excellent result. I might add more cherries next time.
In all cases I have not added any extra sugar but have used Campden, a tsp of DAP nutrient and also pectinase at primary. Probably the most useful information I can give you is "KEEP NOTES", enjoy the tastings and have fun.