You could go either way really. There's no need to make a permanent decision now. A school place will always be available if you want one, though if your preferred school is oversubscribed then you'd have to send your child to whichever school has a place. Equally, home education is always an option. All it takes to start is a letter to the school. I'd go whichever way you think is most likely to suit your son right now, and change later if needed. A few points to bear in mind:
Your child reaches "Compulsory School Age" in the term after his fifth birthday. If he's currently at a preschool and happy there, you should be able to keep him there until he reaches CSA, instead of sending him to school. Just make sure the preschool knows you want to do that; otherwise they'll assume he's leaving as soon as he's eligible for Reception, and they'll give his place to someone else.
If your preferred school is likely to be oversubscribed, you can keep your options open a little longer by securing a place there and then deferring his start. If you do this, the latest your son can start school without risk of losing his place is when he reaches CSA or the start of summer term, whichever is earlier. You don't have to get permission - just tell the school.
Your child can attend Reception part-time until he reaches CSA. Again, you don't need permission for this. Once he reaches CSA, however, part-time attendance is at the discretion of the headteacher, and most are not keen on it.
It's helpful to have spent some time with other local home educating families so you know what's on offer in terms of social and educational opportunities in the home ed community, and also for chats about other people's experiences. For example, most families find that four year olds don't engage very well with formal education and prefer learning mostly or entirely through play, so you might want to put Twinkl etc on the back burner for now. But all children are different, and you can experiment to see what suits yours best.
Another benefit of meeting some home ed families is that you'll have a more realistic view of what it could be like. Parents who take their kids out of school often say they wish they had done it sooner. If school isn't working, it can be easy to fall into the trap of giving it a little longer and a little longer in hopes that the child will "settle". It doesn't help that you'd be surrounded by other people who don't know much about home education, whose only answer to school problems is to persevere. That's the only advice you are likely to get at the school gates and in meetings with school staff.
Anyway, listen to your instincts. You've been doing that since your little boy was born. You know him best.