I am also new, so you may find my progression interesting. I started with country wines last January. Raspberry, triple berry, Dragon's Blood, etc. Then I thought kits might be the next thing to try. I followed them as close to the letter as I could. After the first 2, pitched on the same day, I started asking the same questions as you.
For the next 2, also both made at the same time, I followed the directions exactly on 1. It was off dry and had a secondary flavor pack, so I added all the other kit ingredients. The other one I only added k-meta, none of the other kit packs.
The last 2 I made I opened up the kit ingredients just to take out the yeast. I have always sprinkled my yeast, so I continue to do so, but other than that I made the kits completely without their additives. I racked to secondary around 1.010. I gave them enough time to age that the clearing agents were pointless, I don't back sweeten and was concerned of off flavors from the k-meta/sorbate pack. I'm a strict believer, if you don't need it, don't add it. It's just another variable to question later if there are off flavors or any other issue. I add k-meta as a solution I make with powder from the LHBS. I dissolve it in a shot glass and I don't bother to stir.
Of the last two kits I did, one had a large secondary flavor pack. I am ready to bottle and I intend to add some to taste in a glass. I want to see how the kit was intended to taste, but I no longer care if I make the kit taste as it was intended. I am making wine the way I like it, which is mostly dry, so I will test it to see if I surprise myself and prefer it back sweeted. If so, at this time I will add the sorbate. 4 months after the kits 'ready to bottle date'.
I have 5 more kits that I intend to put in primary in the next week or so. One is a fun wine. Island mist, or the like. I intend to make it per kit instructions and bottle within 4 weeks. The other 4 are reds, Pinot Noir, Malbec... These ones I plan to forego all kit rules and instructions to see if I can pull more flavor than the very reliable EC-1118 added to most kits. This yeast offers great success rates, but does not enhance the berry flavors, spice notes, and nuances of the specific varietal (grape). I will be using yeast with higher nutrient requirements, so I will need to add nutrient and watch them more closely.
The last 2 kits that I made that are now ready to bottle based on how they taste, were slated to get bottled a couple of weeks ago. I was worried I had disturbed some fine lees, so I let them sit after racking. When I shine a flashlight through the Pinot Grigio there are suspended particles, I don't think they will drop. There is no sediment on the carboy bottom after 2 weeks. Perhaps this is the protein
@winemaker81 mentioned. Either way, I plan to filter before bottling. It is clear, just not 'crystal clear'.
I think everyone else has answered all your questions. I just thought you might find 'what I do' as a beginner relatable.
If I had the option, I would move on to an FWK kit, next. I am not in the US so I can't get my hands on them. I plan to give juice buckets a go next year. If that goes well, perhaps I will look into getting grapes. Like you, I am taking the progressive approach, and not jumping into the deep end without getting some bearings.