As a rule, the less you add to the water, the better. This does not mean everything is bad by any means. It means you should only be adding what you actually need as opposed to what a manufacturer tells you that you need.
I have excellent well water and I add nothing to it for most of my fish. Even though I do not need dechlor for my tanks, I keep some Prime and Amquel on hand. I use it after bleach dipping plants or when I travel to weekend fish events where I will need to dechlor hotel water. However, I have live plants in some tanks and plants need fertilizers. So I add some of these because the water out of the tap and the fish don't supply all of what the plants need.
I have a tank for Altum angels which need acid water. So I use RO/DI water, some muriatic acid and a few botanicals to provide what is needed.
I do not like any product which claims to help the slime coat of fish. I especially do not want aloe vera in my water. I also know that most of nitrifying bacterial additives do not contain the proper strains of bacteria that persist in tanks long term. I know Prime contains something to "help" with the slime coat but at least it isn't aloe vera.
My decisions are based in the science I have read on the various topics at work.
I would not put the Fluval product in any of my tanks ir it were free and even iof they offered to pay me to use it. There is 0 need for this product and I know it does not contain Nitrodpsira bacteria which are needed in tanks. Water changes do not deplete the nitrifying bacteria.
Stress Coat contains aloe vera. Therefore, it is on my never use this product list. You must decide about Aloe Vera for yourself.
I do not see the need for Stresszyme or any similar product. My tanks work great and have for 21 years without ever using this sort of additive.
As for ferts., there are a lot of choices. I have used Tropica prodducts for almost 20 years now and have been very happy with them. I have tried dry ferts and i do use some of the SeaChem individual ferts in bigger tanks. These are a pridier options but the convenience makes them worth it for me. Planted tanks are something one needs to work out the fertilizing routine over time. Every tank is unique and it is a question of figuring out what the plants one has need to keep them thriving.
Finally, as far as I know most of the big online suppliers offer autoship on all their products. If what you have is working why change?