Hi and welcome! You sound really motivated to figure this out! What book did you order? Different authors take different approaches. I think Patrick Holford is the only one I've seen who advocates keeping a strict count of GL through the day but there may be others. I tried the counting approach some years ago but it wasn't for me personally as there was too much for my brain to keep track of.
Most of us in the forum have found our success in taking an approach of just making good low GI/GL choices, some of us with an eye to calories as well (using myfitnesspal or similar to track). This could be considered closer to the 'traffic light' approach where one eats as much as one likes of 'good' stuff (keeping an eye on recommended GI/GL portion sizes of good carbs), tries to only eat medium GI/GL foods infrequently, and avoids high GI/GL foods as much as possible.
I don't personally think there's anything wrong with a skinny latte every so often although some authors recommend against caffeine - I think people have to find what works for them.
Where low GI/GL differs from plans like WW or SW I think is in snacks. For example SW would say go ahead and have a freddo, it's in your syns. Low GI/GL would say that the freddo will mess with your hard-earned blood sugar stability because of the sugars/carbs and level of processing and that it would be better to have a couple of squares of dark chocolate.
That said I feel that for me it's been a very liveable plan as you can make it work for you rather than strictly following a set plan. Although if making it work for you involves following a strict plan then there are plenty of them around to follow too.
Sorry I've babbled on since you had already found the answers to your specific questions. Anything else, just ask! Although it will probably be quiet here until after the hols.
Good luck with your weightloss journey; I hope you'll join us here for it.
