One year old is a good age to neuter, no problem. It won't change his personality - that's a myth. I think a lot of people see a change in behavior because we generally neuter when the rabbit is a teenager and the apparition of the adult personality is wrongly attributed to the neuter. I've never seen the slightest change in behavior in any of my rabbits after spaying / neutering... except for, you know, no more humping / spraying / growling and stuff ^^.
A big no to the idea of bringing a second male. I've known a couple of people who did it successfully but it generally doesn't work and even when it does the pairing is generally not stable (fights occur regularly because a top rabbit is difficult to establish with that kind of pairing so, you have to expect regular coups except if you lucked out and got a very dominant buck with a very submissive one - if you search the forum, you'll find a plethora of threads called 'Help, rabbits are suddenly fighting!' and yeah... it's great you're asking before attempting anything ^^'). I think the problem is that it's not a natural configuration. Warrens are matriarchies and the top rabbit is almost always female... this is why 2 females is also an unwise pairing to attempt, as females can be very territorial. A neutered male welcoming a spayed female (don't put an intact female with your buck even if he's neutered, they will fight and he will attempt to mate anyway which could end really badly) on his territory is the best configuration possible. Bucks are generally delighted to have a doe on their territory (it's not always true in reverse ^^') so chances are it will go well pretty easily. If you can, getting an already spayed female from a rescue would be ideal (age and breed don't matter) as you won't have to wait until she is old enough to spay (around 7 months) and after she heals (about a month after surgery) to introduce them.
My opinion and experience differs. It's inaccurate to say that a change of personality after a neuter is a myth. It might not be what you personally have experienced, but you can't just say that others accounts of this happening aren't true and that it might have had nothing to do with the rabbit going from teenager to adult. And I can verify this statement as fact since it happened to one of my rabbits who was older when he got neutered, so has nothing to do with maturing from teenager to adult. I can tell you that it is not a myth and can in fact happen. It doesn't usually happen, but it certainly is a possibility.
It's also inaccurate to state that you shouldn't put a neutered buck with an unspayed female or they will fight. Sure that could happen, as it could also happen with a neutered buck and a spayed doe, but there are plenty of instances that I know of, where no fighting occurs and the rabbits get along just fine. Again, this is from my own experience of having a neutered buck bonded with an unspayed doe for some time until I could get her spayed. They got along perfectly fine, never fought, and were perfectly happy together both prespay and post spay. I also know of others that have had an unspayed female with a neutered buck, without any issues occurring. It's all down to individual personalities. It's usually not recommended, especially for beginners, as fixed rabbits won't have the hormones complicating the bonding process, but there are instances of it working out fine. This isn't to say I don't recommend getting pet female rabbits spayed. It's best for their health, but I and other's have successfully had fixed males with unspayed females until the female could get spayed.
As for pairing, male/female is usually considered the best, but it really all comes down to the individual personalities of the rabbits and finding the right match that way. Though male/male and female/female pairings are considered to be more likely to have issues, it's not always the case and there can be m/m f/f that get along great. I had two females together that were perfectly happy and never had issues, I also have a group of 6 that contains 3 males that get along perfectly, and know of others that have m/m pairings that worked out just fine. It's just all about finding the right rabbit for your current one. You could have a female/male pairing that ends up being a disaster if you don't find the right match for your bun. You need to find the right match of personalities regardless of gender.
Bunny dates really are the best way to go. If you could do it in your own home in a neutral area where your rabbit hasn't claimed it's territory, that of course is ideal. But it doesn't usually work out that way, and most often you have to take your rabbit somewhere for the date. Or you take a risk and just bring a bunny home and hope for the best. If you can't return the bunny if it doesn't work out, you need to be prepared to keep both rabbits separate, or to rehome the other bun.
Lilnaugrim, if you opt for bunny dates, I would suggest trying for love at first sight if at all possible. A difficult bond can be quite stressful, especially for a first time bunny owner, and a love at first sight bond is less likely to have the risk of a falling out at some later period.