Yes, they go well with tetras, however, I would be weary about guppies. There long tails can cause them to become aggressive, thinking they have to chase off a potential rival male. Ive found though, that it really depends on the individual fish though.
Bettas and guppies are commonly a huge no no. However personally I think it depends on the Betta. As Bettas have bad vision and will see the guppies long flowing tails as another betta they will flare and attack. However I have had 2 Beeta who's personallities have been completly different.
Rambo - My first betta passed away 4 months ago at the age of 2 - Really aggressive betta, when i started my 40 gallon i have 10 glowlights and a betta, the betta would inhabit the upper half of the tank however he would also come down and flare his gills at the tetras and chase them. I had to eventually move him from the tanks as he killed 7.
Rockey - Current Betta - Rockey at the moment has white spot but it improving in his condition. However this betta is very peaceful. He will inhabit the upper half of the tanks but will also come down and swim along the bottom. However he has never flared at any fish except the mirror that I placed next to him once.
Betta's are wonderful and depending on the fish they will either be peaceful or aggressive.
I personally wouldn't put a betta with guppies as they are like to nip their fins. However bettas and gouramis have no qualms with eachother the cohabit the top area of the tank in peace. Probably because the gourami is bigger than the betta lol.
i would seriously advise against putting guppies with gouramis, my powder blue was totally peacefull umtill i added a guppy and the poor guppy tail ended up shorter and bloody. Please dont do it.