I think two males tend to be the way to go. I've only had a couple cockatiels before, but with budgies males get along really well with each other. Two females can work, but much more room for fighting and attacks. Male and female together leads to babies and to randy males attacking females so that just results in more fights and bickering. I find two males to be the best for most pets (cats and dogs are the same way) but there are exceptions with all pairings.

I love the look of cockatiels but I was never a huge fan of keeping them, way too loud for my taste. They are chattery like budgies, but louder. Same with lovebirds. Parrots are loud but don't chatter as much, and budgies chatter a ton, but are quieter. I'm to trying to sway you or anything, just talking about birds haha I really enjoyed raising them. I haven't had any in like 8 years though. I just got tired of it after a while. I never had a pet bird really though, they were always for raising. No I guess I did. My pet budgies died, very sad. And I had a pet ring neck parakeet for several years but he was really mean and never liked me so I eventually sold him, the lady I sold him to was like an expert bird raiser, I was hoping she could tame him more