You're asking good questions. One thing to be aware of is: there are an infinity of combinations of equipment, media, fish, and general practices to choose from. Many of them work.
When narrowing down a system, you may be overwhelmed and distracted by these combinations. It can even be counter productive.
I would say, assuming you know what fish you will keep, any offbeat needs they have, and you have chosen a filter suited for your tank (it can pump and filter the full capacity of your tank 4 times per hour, or 80 gph
), you should be able to trust it will work if you follow the directions. Maybe look at reviews of that filter to spot recurring concerns among owners.
If you've followed proper cycling and indications are your levels are right, you should be fine.
Good luck and have fun!
1. If you don't have a user manual for your filter, I bet you can find a PDF of it online. It's bound to help a lot. And companies often answer questions when you email them with a brief request -- a simple question they can answer easily.
2.There is a common belief that manufacturers push aquarists to replace filters and media too often. It's is heard often, everywhere, so keep it in mind.
3. Your media combo will be flexible. You can change it. Don't think you have to aim for perfection in a totally optimized tank. Set it up as instructed; ask around if you need, but beware of 100s of opinions that can slow you down. Adjust it later if you learn something; leave it alone if it works. The fish will be fine.
4. An interesting tip I picked up recently: if you are setting up a new tank, get a small piece of media already in use in another healthy tank. Perhaps from a friend or even a store. Just ask. Evidently this will skyrocket the speed in getting your bacteria up and running where it should be, much much faster.
5. Last, know the absolute exact *interior dimensions* of your tank, not counting glass thickness. Hand measure it yourself. It is the only way to know its true total capacity, and hobbyists are strangely incurious about this. Boxes, product listings, online specs are often very very wrong -- often they are exterior dimensions (for fitting it in a space). And don't buy "inches" of fish based on 100% capacity -- factor in the water fill to brim distance, and the height of substrate Add them together and multiple them by the interior length and width (floor area). That is the cubic in. volume of the water displaced by "earth and air." And use the size of the fish when grown -- new fish are usually juveniles and not yet fully grown.
Hope you find something here useful!