Hi! Do you know the tank capacity in liters? Or the tank make and model? The size 10 gallon is often attributed to a few different sizes due to the confusion of imperial and metric gallons and also some manufacturers have them rated as if the whole inside would hold 10 gallons including the lid space. I have seen tanks called 10 gallons that range from 33 liters to 64 liters - ideally I am hoping you have a 64 liter
Reason I ask is some of these tanks could be fully stocked with 6 guppies. Especially if you have a mix of males and females.
In small tanks like this I prefer to stock them using micro fish. Most larger fish have smaller relatives. So instead of your Guppies I would have gone with Endlers, they are much smaler and just as colourful and look like mini guppies. In this mix you can add thinks like Galaxy Rasbora, Chilli Rasbora and Sparrow Raspora all are classed as Micro Rasboras and stay small which allows for larger schools in smaller tanks. Other options are Ember and Green Neon Tetras which are also quite small fish.
For bottom dwellers you need sand in a tank this small, but you could look at things like Pygmy Corydoras, Rosy Loaches and Dwarf Anchor Catfish. Though only 1 group of 1 species.
For some oddballs you could look at Cherry Shrimp or even if you can find them, Thai Micro Crabs - you could also get an assasin snail which will deal with your snail problem
Most of those fish would work with your guppies it just depends on how much space you have in there
An other way to deal with the snail problem, simply put a lettuce leaf into the tank and weight it down, turn the lights off, leave it for about 20 mins come back and it should have snails on it, take it out, throw it away with the snails and repeat until they are all gone
Wills