Hi and welcome to the forum
What do you mean by bio vs non bio system?
Plecosotomus catfish can grow to 2 feet long and regularly hit 18 inches in aquariums. They should not be kept in aquariums.
If you want a small suckermouth catfish, look at bristlenose (Ancistrus sp), Peckoltia sp, whiptail catfish (Loricaria sp) or twig catfish (Farlowella sp). These are much smaller and grow to 3-6 inches and will be ok in an aquarium that is 3 foot long or bigger. Do not get any algae eating catfish until the tank has been set up for a couple of months. They need algae and biofilm (slime on glass and ornaments) as part of their diet and there won't be any in a new aquarium. They also need driftwood to graze on and help their digestion.
Guppies come from water with a GH (general hardness) around 200ppm and a pH above 7.0. They do best in tanks that are at least 2 foot long. Try to keep males or females and not both because they breed prolifically and if you have females, you will get babies. Then you will need a bigger tank or a second tank.
Betta splendens (Siamese fighting fish) are best kept on their own. Some will get along with other fish but others will kill anything else in the tank. There is no way of telling which fish will be ok and which won't be ok with other fishes. They come from water with a GH below 100ppm and a pH below 7.0. They do best in aquariums around 18-24 inches long.
GloFish tetras come in a few different species and it depends exactly on which species you want. As a general rule, tetras should be kept in groups of at least 10 (preferably more) of their own kind and kept in tanks that are at least 3 foot long. Some smaller tetras can be kept in 24 or 30 inch tanks but they do better in bigger tanks. Most treats come from water with a GH below 100ppm and a pH below 7.0.
For the fish you are looking at I would go for an aquarium that is 3 foot long x 14-18 inches wide x 18 inches high. It will give the fish plenty of space and allow you to have a variety of different species.
I would not keep guppies with tetras and I would not keep Bettas with anything else.
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What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
