Honestly, it just seems to come naturally either way. It definitely has its challenges having two more children but so doesn't having just one.
My two oldest kids are three years apart and I liked it that way because I didn't have 2 in diapers at once and one was on a routine while I was getting the baby on his routine. She loved her little brother and didn't show any jealousy at all. The biggest challenge for me though, was I did feel like I couldn't spend as much time with my oldest because I was so busy with my baby. Babies are demanding and require a lot of time so you just have to get in that routine of having your oldest help you with the baby and when the baby is napping spend time with the other child. It leaves little time to you or you and your husband but they aren't little very long.
Being home with them for the first time takes some adjustment but you get used to it really quick. Don't be afraid to ask someone for help like your mom a friend or someone close if you need it until you get in your own routine. Another big challenge is going somewhere outside of the home with two small children, bigger diaper bag, more car seats, more stuff to carry, especially if you are alone, I liked having them a couple years apart because when I was carrying the baby to the car my daughter could walk I didn't have to carry them both or leave one in the house and take one of the car etc. some people like having them close together because you can try to get them on a similar routine.
The further they are apart the less they share when they're older. All siblings fight though no matter the age gap.
My baby is 9 months old and there is 12 years between her and my son and my two older kids are such a huge help with her. But now me and my husband have been talking to about when to have another one or if we even are and what the gap will be between them.

My kids are five years apart. I never had to worry with jealousy, it was just me and my son for a long time so he cared for his sister and understood that I needed to care for her. He was a huge help with her. It was nice having them so far apart. The bad part, they don’t have toys or shows they share, they fight a lot because they are at different levels mentally.

The reasons you listed off for worrying, are not reasons to worry. Most kids want to show their new sibling as much love as you do. At least at first. And jealousy is always going to be a concern, but it helps the child learn that the world doesn’t revolve around them. Also helps them learn to care for others. As far as caring for them both at the same time and so one, it’s like riding a bike, you will instinctively create a routine and you’ll roll with it. Don’t think about it so much. If your ready go for it! There are pros and cons to having them close and for having them years apart. Mine r five years apart and my best friends are 10 months. Hers act like twins. But really it’s all the same!

The best time is really no best time . You tend to make it work . I think if you guys plan it which is what you're doing now then being prepared can help . but so far I've been just going with the flow. Making sure I spend time with my one year old even though most of my time is spent with my 1month old. I'm at home by myself a few hours a day but we manage . my son isnt too much of hassle other than typical toddler behavior . so that makes it a bit easier. Also getting help from family and friends is a must of possible .