as said before its down to individual fish, my betta lives with other fish and he's fine, also it's what the other fish might do to the betta, so if you're going to attempt fishy friends you've done the right thing by researching.
Also if you're going to do it have a backup plan ready, spare tank or tank divider!
In my experience tetra are not good friends, they are nippy and this can cause finrot issues, barbs are nippy also, although some people have had success with cherries, but to be honest i'd not risk even those.
Danios and white clouds make good tank mates, but may stress some bettas out, mine loved danios!
Rasboras make excellent tank mates, they are non aggressive and pretty little fish, I currently have these living with my betta, as well as a pitbull pleco.
Small bottom dwellers like pitbull or bulldog plecos are good tank mates, and many people keep cories as betta friends.
Guppies are to be avoided as bettas can misread them for competition and injure guppies, also if you're wanting any fish babies the betta will not be a good addition as they eat young fry, i've witnessed this when my danios used to spawn!
but have a think, and have a go as long as you have a backup
