I have used this magnetic PEI spring steel build plate https://www.amazon.com/gp/product/B08B4CBY9C/ on my Ender 3 for almost a year and just bought another for my new Neptune 2. The PEI surface on my Ender 3 one is starting to wear a bit, but I was happy enough with it to get one for the Neptune. I originally had the Creality glass bed on my Ender, and really liked the convenience of the magnetic plate over that. I mostly use PLA and PETG, if that matters.
the Microswiss extruder is plug n play, just a different design than the stock extruder. It comes with all the needed parts to work with the V2 Neo, which I can confirm since I use it without issue. If you have a filament guide you might have to find a different design as the MS extruder moves the path of the filament to the other side of the motor shaft, so it moves it about 1cm. But even with that, it's completely plug and play with a stock v2 neo. My esteps are just higher now (136 i think?) since the gears/teeth ratios are different but that shouldn't be something you can't handle at this point.
The heatbreak I shared with you works. I cannot say if it's great or if there are better options (probably), but I can at least confirm it works better than stock and combined with the MS extruder I RARELY get clogs now compared to stock where I got them nearly every other print. I also used boron nitride paste to help fill the gaps and conduct heat more evenly (like heatsink paste)
and since I'm enjoying sharing what upgrades I've had success with, also look into this style of thermistor once you're fed up with the glass bulb version or yours dies. This screw in style is so convenient. I soldered the plug near the hot end so I can now plug n play swap thermistors without soldering again next time. Haven't had to replace this one yet, but when I need to it'll be super simple. https://www.amazon.com/gp/product/B08YNX79H8
And then I've upgraded my bed to this PEI sheet and adhesion is almost never an issue these days https://www.amazon.com/gp/product/B08B4CBY9C
I'm currently in the process of a cheap upgrade to add an antibacklash nut + oldham coupler to the threaded Z rod to absorb some of the imperfections in my rod (lulz). If I have good luck with that I'll share some details but the seller sent me the wrong size oldham coupler so I'm process of having that replaced first.
Any of the parts I'm sharing i can confirm are the right size for a neo, but i'm sure there are other options and sellers. So I'm not trying to sell you on of these links, just giving them as a reference/suggestion. Except the microswiss extruder, that I'll shill for any day because of how much of an improvement it has been.