More battery life is *always* better, but I really have no complaints about my Note 10 battery. It lasts all day, every day. I average 5.5 hours SOT, but it would get a lot more if I pushed it below 10% charge. However, I rarely let it drop below 30%, or fully charge to 100%. I try to take it off the charger between 60-80% to preserve long-term battery life. So while 5.5 hours SOT may seem low to other Note users, I am averaging 5.5 hours SOT from only a 50-70% charge, which is pretty damn good imo.
I disabled some apps that I'll never use, but otherwise I don't need to gimp it to make it through the day. I noticed a slight improvement in battery life with Android 10. I don't do much gaming, but I do a lot of web browsing, YouTube, and listen to Google Play Music and Sirius XM, and it has no problems lasting a full day.
I have the Snapdragon model. I don't have any experience with the Exynos model, but if you are in the UK, then I would recommend going with Exynos just for the warranty. There may be some YouTube videos comparing the battery and performance differences, you may want to look for those. I remember a couple of years ago the Exynos models were noticeably worse as far as battery, but I think the latest Exynos chips have closed the gap.
If battery life is a top priority, then you should consider the Note 10+ which has 23% larger battery (4300 vs 3500 mAh).
One last thing to consider: The Galaxy S20 models are right around the corner. I am not trying to talk you out of a Note, but if you can live without the Spen, you might want to wait for the Galaxy S20 Plus and Ultra. The Plus model is supposed to have a 4500 mAh battery, and the Ultra is rumored to have a massive 5000 mAh battery.
Edit: Btw, congrats on graduating from iOS. You'll love the customizability of Android, and now that RCS is available, you won't miss iMessage as much