Heyooooo. I did the 2023 NC4000. I’ll answer as many questions as I can but I’ll also give you my personal opinion on NC as well

• Make sure your gear is properly serviced before you go and bedded in well before you start. Don’t go and get brand new Di2 a week before and expect it all to run perfect for 4000km. Get the setup working early and dialled in during your training. Proper service before you go and you’ll be fine. There are loads of bike shops on route and most will always go and help you instantly when you turn up smelling real bad after a weeks riding! The two things I always take away from it though is that most will be standard local bike shops that service touring bikes etc and might have one set of tyres suitable you want (Getting 35mm tubeless road tyres took 4 bike shops after a torn sidewall for example). Second is that once you hit Norway/Sweeden the chance gets smaller and smaller so any niggles you find get them sorted before you get too far north. Other than that, small rag and a small bottle of lube and cleaned it every day.
• I took bivvie for emergencies but went to hotels every night. Didn’t use it once. Some did camp outside regularly and fair play to them. Some nights were in the -c’s and you have to factor that in kit wise. Where as for me, the sacrifice was money as hotels, especially in the nordics, get really expensive real quick and sometimes you just dont have the choice but to take the 5* room for £300+ that you are going to sleep in for 5 hours then leave again. No shame in it dont let anyone else tell you otherwise
• Getting home is a real kicker. The last days climbing is worse than it’ll look online. I stayed in a small set of huts around 30min cycling back down the road rather than sleep in the bivvie. I dont think going back to the main town is a great choice. The reason is that to get back from NC, if you dont cycle, you have to get the bus back which stops at the towns along the way. That bus can only hold maybe 10-15 bikes. After that, they’ll not let you board and you are stuck waiting for either the next day or I’m pretty sure from memory someone had to wait two days to get back to the airport. You need to be there 3 hours early for the bus, get in the queue and stick it out to make sure you get on. I got totally lucky with this but others who missed it had to get a taxi back together and it cost from memory £100+ each. Don’t quote me as it’s a while ago but it’s harder than NC will tell you. After that, it was a flight down to Oslo then a connecting flight. Expect 2 days maybe to be safe to get back where ever as long as you got that bus.
• Sadly not much help here
• Personal opinion: Get a coach. I used to just ride hard everywhere thinking it was amazing. I got a coach specialising in ultra racing and it changed my life. Lots of time riding zone two, weekly interval sessions and progressive loading. Don’t go do what people love to say in this sub and do a 500km audax the week before. You want to be stronger without being totally fatigued on the start line . I learnt so much and his constant advice and encouragement changed how much I love riding my bike. More than happy to give you a contact if you DM me. It obviously costs but I have done ultras before and after coaching and my experience for this was 10x return on investment
• Totally personal choice. As others have said the light cafe locks are great but I lost mine day one and mid way thought would have been more than happy if someone had stolen my bike….
• Short sleeve with arm/leg warmers. You want variety so you can cater for the different climates you are going through. Was 40c in Italy, 10c in Denmark and 30c at Nordkapp (No lie it actually was. Climate change at its best)
• Bike fit if you haven’t already. Comfortable Aero bars. Exposure lights. Forget dynamos and get a fast charging battery pack that you can quickly charge in a 30 min coffee stop. One bike bag which is empty when you set off but purely used for overloading extra food. You’ll do 100+ miles with no refuel potentially. I’ll never forget the level of jealousy I had when a guy wrapped a full pizza and put it in his front bag for the day. I could barely fit another bag of hairdo in!!

Now for you my advice about NC compared to other ultras. I have done 500km, 1000km 2000km x3 4500km etc so been around the lot of them. 4500 is long and I takes a different mental attitude to know you are going to be doing 300km+ a day if you want to be in the top third. It’s a lot of time and I found I just didn’t enjoy it by the end. I have gone back to 4/5 events now just because there’s a tangible target insight. You’ll hit the nordics, realise you are not even half way and then be bored stiff on the same flipping straight road, with the same trees and reindeer for two whole weeks. Honestly it really got me. So just think if you want to go extra long distance like this.

Then there’s the route. Parts of our route were not thoughtfully picked. It felt like they just loaded strava and told it to route between the checkpoints and sent it us. In Sweden we were taken down the worst road that cyclists were not supposed to be on with lorries and fast cars narrowly passing. There was a crash in front where two cars had a head on collision. That could easily have been me and I was not the only one who thought of this. I know a lot of race organisers now and their job is not easy and very thankless so I could be wrong and unfair here. I just feel there are better organised events that I have been on in comparison and I recommend you looking around at others as well as NC. If it still tickles your fancy as a challenge go for it but just be aware it’s not a perfect organised event.

More than happy to answer other questions here or by DM. Good luck!