You have 96 liters of volume there, assuming no displacement from decorations and you are full to the rim

This is as near as makes little difference 20 gallons.
This means you need a 100 Watt heater. I personally favour Visitherm for internal heaters, and Hydors if I'm using an external canister filter

this said, Hagen Elite, Fluval Tronics and Tetratec heaters have all served me well in the past. I would avoid Superfish heaters like the plague though, their average life span with me was 1 month, after 5 replacements, I gave up and switched brands
For filters, you have two "main" options and a couple of side-lines. The main two are Internal and External (also called Canister) filters. HOB's would be one side-line option, but harder to get here in the UK, along with UGF and all manor of air driven filters

UGF are the best for biological and mechanical filtration, but are high maintenance and can be hard to work with. Air driven filters may be the cheapest to run, and are good for biological filtering, but they are noisy and not great at mechanical work. If you are interested in any of the "side-line" options, let me know and I'll do yo are write-up on them in more detail
External canister filters are my filter of choice wherever possible these days, but they are more expensive than their internal counter parts. They are silent (the good brands like Eheim, Tetratec and Rena) and really low maintenance, needing attention at about six monthly intervals IME (Bar Fluvals that seem to need weekly attention when under the same load with the same pump ratings :shrug: )
Internals are cheap, but usually need weekly or fortnightly cleans. They are good for mechanical filtering, but biological, the most important filtration the filter does, can be a bit weak on many models due to a lack of filter media. Fluval's were my make of choice for internal filters when I used to run them
If you choose the filter type you prefur, we can then help you pick the make and model for you
HTH a bit
Rabbut