Hi and welcome! Which country are you in? It will make quite a difference to which options are the best and safest for you! please click on your username on the top bar, then go to personal details/location to add your country, state (US/Aus) or general area (UK). That will help us greatly in giving you the appropriate information and recommendations straight away!
Trios are great if they work out, but unfortunately unless you get the character combination just right, they are more likely to end with an outsider problem of some sort than not. Baby boar trios have about a 90% fail rate during the first year before they reach a more settled adulthood. If you are really keen on a trio, I would recommend to date or rehome a neutered boar /2 bonded sows trio from a rescue that has both and can safely bond or date them for you so you can be sure that they get on well and complement each other.
Otherwise, I would strongly recommend to rather start with an already bonded pair of either sows or boars. You can get a separate pair of boys later (boars are best kept in pairs) or add/date a younger pair of sows to your own sow pair if you want to get more. That way, you neatly avoid any outsider problems.
Neutering is only recommended if you have a vet on hand that has a good track record in guinea pig neutering; otherwise the risk during the operation and especially of post op complications is much higher. Your neutered boy will also have to wait a full 6 weeks after the operation before he is 100% safe to go with sows. I have the surprise baby from a supposedly safe over 5 weeks post op boar, just to prove that it really can happen as late as that whatever a vet may tell you - and I have heard of several other cases since!